IMHO, the best guidebook is probably West Australian Rock (2002). A little dated but covers a lot of the classics. Probably still available in one of the outdoor stores (eg. Mountain Designs, Mainpeak, etc) or perhaps at the climbing gyms.
Check the book out for climbing grades. Plenty of sports routes in the Promenade, just be prepared for some steep stuff.
Temps might be good (cool) in July but could also present some rain. If it rains too much they do shut the road into the gorges. I think the wildflowers start in July (if you’re into that sort of thing).
Hope that helps a little.