If you are not looking for anything fancy, just a place that is clean, has AC, hot water and wifi, the two places that I recommend are Mar de Cortes, and Quinta del Sol. Between the two, I like Mar de Cortes for its location, since it is right in downtown, a short walk from the marina, and it is easy to walk to decent places to eat - both on the local side and the touri$$$ty side. Quinta del Sol is slightly nicer, but is a 10-15 minute walk from downtown. It is a safe walk tho, since it is right on the main drag, Lazaro Cardenas, that leads right into town.
If you are looking for something a bit more upscale that is also centrally located but won't break the bank, the only other place I have stayed in has been the Tesoro Hotel - they are right on the marina.
August is hot, hot, hot. It is also hurricane season, but nowadays the weather worldwide is crazy and hurricanes have struck there as late as November, so it is a matter of luck. There is probably no season there that is safe from hurricanes except for winter and maybe spring.