Hi Greg:
Herself and I were in just the places you mention last August, looking for roughly the same set of species. We had a pretty good time, but found the birding very frustrating - birds are just so much more skittish there than we are used to. A scope - even a little travel version - would have been so useful (alas, we were camping, already had a heck of a lot of gear, couldn't really fit in the tripod as well).
ANYway - some good sites that we found:
Croix de la Crau: From St-Martin-de-la-Crau, go east on D113 about 8 km, go around on the roundabout to the third exit, bearing NE - I believe this is called the D25B. Right near the intersection, there are a couple of farm tracks on the right; we took the first, but I suspect we would have been better off on the second. We ended up in an orchard, and had to hop a drainage ditch to get to the good habitat. I think that the second track leads right into the stony habitat that you're looking for.
Anyway, this was a nice, quiet place to look at a number of rather distant birds. However, we did see Lanius meridionalis (I think that's Iberian Shrike) there, Tawny Pipit, and a couple of wonderful European Rollers. Hoopoe, however, was my best find... just because it's such an outlandish thing to look at.
We also tried the area south of Vergiere, a.k.a. Réserve Naturelle de Peau de Meau (from the N568, go east on the D24, then right on Ch. d'Istres a l'Étang de Aulnes; after a few km., keep left on the Ch. de Aulnes, rather than continuing straight on down the driveway to the Chateau de Vergieres; the split comes about 500m. before the Chateau).
We only had an evening there, but it could have repaid a much longer visit. Good close views of more rollers here, and many kestrels - but try as we might, though, we could not string any of them into Lessers. Little Bustard is supposed to be there, unfortunately we dipped. However, if you get there early in the morning, before the heat haze really cuts down the visibility, you might do better than we did.
Dipped on Sandgrouse in both places too, but that may be a question of the time of year - I think they're resident, but are more conspicuous sometimes than others, and August just is not a good time.
Cheers,
Peter