Jerome,
I did the camino May last year. It was hot. No rain in Galicia at all, only fog. But snow at the Cruz de Ferro.
I don't know how you define 'too many people' on the camino, but if you will be walking slowly (and I suggest that you do), you'll be overtaken by hurrying pilgrims every few minutes, especially in the Galician stretch. Just greet them buen camino or hola and let them be with their race towards the refugios and inevitable blisters. In my 33 days of walking I only ran out of bed once, in Viana, and that was because I stopped at 5 pm, a bit late by most pilgrim's schedules -- not enough time left to dry the laundry.
By the way, I noticed that in the last 5 days to Santiago, those who began in SJPP seem to be dragging their feet, not because of the foot injuries, but probably because they don't want the walk to end soon, whereas the ones who started in Sarria still have that bounce in their walk; these are the ones who walk straight regardless of the stones on the path.
Mark