We were in Yellowstone in mid May. It was the perfect time IMO. Weather was high 50's or low 60's every day.We spent 4 days in the park and should have had 2 more. We stayed in the park at Madison. I too would suggest staying in the park. The park is about the size of Rhode Island so you will be doing more driving if you stay outside the park.We saw a grizzly mother and 3 cubs on the road from Norris to Canyon.We ate dinner in the Inn at Old Faithful which is the largest log structure in the world. The lobby is beautiful. There are no campgrounds in between Yellowstone and Grand Tetons. You go from one right into the other.But GT has a few nice campgrounds on it's own. I agree with the others that trying to hit Glacier on the same trip will be pushing it with the amount of time you have. Yellowstone will be very crowded in July so getting around will take more time with the traffic and buffalo jams.
