In reply to shaun walby:
Late May for valles de trubia will be great in terms of temperature. You may catch, thougth, a bad spell of weather and have a lot of rain. There are, however, same places that you can still climb, but probably not in the grades you are looking for.
The other advantage of late May is that it is outside the main holiday season so less people. It may be a bit hot to climb in the sun if the weather is particularly hot, but if this happens you have a lot of areas with shade, at least some part of the day.
If you go be sure to visit Marabio, for climbing or just sightseeing day or night. It is a really nice place.
Have fun.