Terrabella, I'm not sure where you're from in Tx because it's in the 90's-100's everywhere now. I'm in Houston, averaging 100oF from about 12 to 5 every day. I'll take Liesl out for morning training at 645 (she's hungry, fresh, responds well) and then a walk for about a half hour. She stays outside until noon, but we have a small inexpensive child's plastic wading pool full of water for her in the shade and she def uses it. Either I, my wife or son will then crate her inside from 1-5. She's outside again until I get home and feed her at about 6:30, then train/walk again when it cools off a little around 8-9. She spends the rest of the evening inside for family evening time. That is the only way we've found to deal with this oppressive heat and humidity and "do right" by our dog.
Congrats on getting a rescue GSD! The two organizations here in Houston are great. If the biggest problems you have with a rescue are those you mentioned you can consider yourself lucky. I agree with the previous posts about you needing to give your dog what it wants (attention) only when it does what you want. However, I've found that a firm "no" lets them know that the behavior is not wanted, and once they get that, replacing it with a reward-reinforced good behavior is easier. I get MUCH better results when I do this before feeding, as I have Liesl's undivided attention and her threshold for a "high-value treat' is significantly lowered!
Liesl, b. 1/1/11