You might take a look at the Transandalus website. It won't help with Portugal, but it will give you a choice of two great BTT routes through the provinces of Sevilla and Huelva to reach Portugal. The tracks for the entire 2500 km route are free online as are the accompanying route guides. It's a great ride through the mountains and National Parks of southern Spain.

Website: https://www.transandalus.org/#!/

The tracks are also on Wikiloc: https://es.wikiloc.com/rutas-mountain-bike/transandalus-vuelta-a-andalucia-en-btt-366563
https://es.wikiloc.com/wikiloc/user.do?id=430319

Here are some leads to BTT routes in Portugal:
https://biketestreviews.com/bikepacking-in-portugal/

[Optimal Season:]

I'd be glad to help! You could also check the Transandalus Facebook page for some ideas. https://www.facebook.com/pg/TransandalusBTT/posts/?ref=page_internal

Optimal Season: I'd say spring (flowers) or fall (less chance of mud) is best. Summer is hot. Winter is doable, but with the caveat that there could be snow at the higher elevations, particularly in the provinces of Granada and Jaén. WeatherSpark will give you an idea of the average temperatures and precipitation for any spot along the route: https://weatherspark.com/countries/ES/51
Direction: The route guides are set up for the route to be done anti-clockwise. You can start at any point.
Typical pace: Don't go by us! We are without a doubt the slowest riders on the Transandalus! (We like to explore everything nearby and I am not a strong rider.) Some riders do the entire 2100 km circuit in a month. I'd say two months would be a comfortable rate for many riders, allowing for rest days, a little exploration, bad weather, and travel at either end. Maybe 60-80 km per day. The stages vary greatly in terms of difficulty. Here's a blog from a Spanish rider that will give you an idea: http://zinaztli.blogspot.com/2009/08/transandalus-ficha-del-viaje.html. He averaged 70 km a day. There are links near the bottom of his summary page to detailed descriptions that give the exact km he rode each day. (Google translate will help if you don't read Spanish, or open in Chrome for auto-translation.)
Food: Readily available every day in small shops in every village or in restaurants or bars. Shops are closed in the afternoon, 2-5 more or less, but open again in the evening.
Challenges: some technical parts of the trail (I walk these); weather (possibility of high winds, heavy rain, snow) although it usually great; you need to download the gpx tracks for sure (we use https://www.wikiloc.com/wikiloc/user.do?id=430319 and Gaia and have their IGN map of Andalucia downloaded for offline use).
Feel free to contact me for anything else I can help with. Happy planning!

Would you like me to forward your posting to Neil Gunton who runs CGOAB telling him your registration won't go through? He'll get right back to you.

Both sound great! In the guestbook section of our journals on CGOAB, you will see a way to send any questions you might have and I'll reply with a link to our email. Good luck!

Officially, wild camping is not allowed, but unofficially, you can bivouac, setting up camp at sunset and breaking camp at sunrise. Many Transandalus riders do this. The route is beautiful and you will find lots of places to set up your gear. Two times to pay special attention are when you are traversing the National Parks (Doñana and Sierra Nevada). They have strict no camping rules. Natural (vs National) Parks are a different story. Cazorla Natural Park even has several recently restored shelters with water and tables available to walkers and cyclists. They are marked on this map: http://www.sierrasdecazorlaseguraylasvillas.es/gr247/en/index.php?option=com_wrapper&view=wrapper&Itemid=283  (Stages 13-17 of the GR 247 follow the same route as the Transandalus). Although we didn't camp much when we rode the TA, our journals have photos that show possible bivouac spots: entire Transandalus http://www.crazyguyonabike.com/doc/TA2008   Sierra Nevada http://www.crazyguyonabike.com/doc/SpainTA2018 Sierra de Aracena http://www.crazyguyonabike.com/doc/TA2015
I hope you have a great trip!

Scott, thanks for a great tool for researching a trail! I vote for 1 being easiest, 10 hardest. Seems more intuitive.

In the interest of getting all the numbers into comparable terms, I just calculated the km to miles and meters to feet conversions for the TransAndalus. They are:
Distance: 1350 miles and  Climbing: 124,672 feet

Elaine

Scott, that page you put up looks wonderful! Good introduction so more people can know about this trail. Thanks!

Kevin, thanks for posting the link to the photo gallery. There are hundreds of images there, and they keep updating it, so it's a useful resource for planning purposes.

Elaine

I'm glad you had a chance to look at the TransAndalus site, Scott. I think they have done an amazing job of getting all the relevant information on there. For each stage of the route, the amount that is pavement, dirt track, or trail is listed in two places. In the Visor de Tramos (click on the link on the right side of the home page, and then click on any part of the red route line), an extremely useful animated page comes up that draws the route as you watch, both on a map and in profile. On the left of each page, there will be a box (labeled Technical Data or Ficha Technica) showing the percents.  In the Roadbooks, (click on a province on the map on the home page, and then on "Roadbook" on the page that comes up), scroll down the pdf and you will see the same boxes. Most of the Roadbooks are on the web in English now, but for the ones that are only in Spanish, asfalto = pavement; pista = dirt track; and sendero or camino = trail. I'm not sure that you can use those words to correspond exactly to our sense of the words, however, because the 33 km of beach and 44 km of pilgrim paths in Huelva, for example, are classified as "track" as opposed to "trail".

I think Fran will be able to give you overall numbers for the entire route. My rough guess for the Huelva and Cadiz portions would be 20% pavement, 40% dirt track that a vehicle could possibly travel on, and 40% trail that a vehicle could not travel on. We rarely saw a vehicle - or even any other walkers or cyclists -  on any of the unpaved sections.
Elaine

We've recently returned from cycling 2000 km of a great route in southern Spain. The  TransAndalus makes a mostly off-road circuit around the eight provinces of Andalucia. The website, www.transandalus.org, is incredibly complete and most of it is now available in English. It includes all the information needed to cycle the route: maps, GPS tracks, detailed route guides, photos, FAQ's, listings of accommodations, and an active forum (on Facebook) where you can get information from the dedicated volunteers who developed the trail and maintain the site. We thought it was a fantastic route offering gorgeous views, plenty of solitude, the possibility of staying in either inexpensive hotels or campsites, and the opportunity to explore otherwise unknown rural areas of a beautiful country. The people associated with the trail are the best you could meet anywhere - kind, generous, and always willing to answer a question. Photos of our ride are at http://www.crazyguyonabike.com/doc/TA2008