People recommend this route for spring, and I for one would love to see the wild peonies bloom then. However we do most of our Camino trips in northern Autumn and usually leave at the start of September, getting into to Santiago in late October before the worst of the rains hit. This has served us well and we found the vdp to be fine for walking then. But we do leave early in the day and aim to stop before 2 or 3 in the afternoon as it gets you in before the heat of the day really takes over. It also means you get the end of the long Spainish lunch, as we found in the remote places things tend to close and not reopen til very late, if at all.
There are several other threads on doing the vdp at this time and I got in trouble for saying it's not that hard and so won't say it again (except I just did). You can read our blog for the unvarnished truth, you will see I moan about it getting cold and wet up around Salamanca, so be prepared for the change in weather as you go.
