Hi Jackie,
I'm sorry but I don't know that part of Spain. What I do know is that travel by Bus is fairly easy in Spain from my own experience of travelling around Barcelona and San Sebastian and also getting a bus between the two cities when the train line was closed!
We were in Spain at the beginning of June and booked most of our accommodation when we arrived in local towns. There were always beds available but some of our first choice pensions where full and some of the lower accommodation was very basic. The main thing to watch out for is if there is a local festival on, if there is then you will have a real challenge with accommodation and travel. In terms of tourist offices, I seem to remember most medium sized towns having a decent set up with English speaking staff. A similar standard to the UK.
Avila is close to Madrid is it not? I hope you like the heat! A lot of the Spanish retreat from Madrid to the coast in the summer for cooler weather!
Have a great trip.