If you're trying to make it to a reservation add a lot more time. For example, Epcot is a huge park. Most of the restaurants are in World Showcase, at the back half of Epcot. It could take 20-30 minutes to walk to some of the restaurants from the front entrance.
Don't let me discourage you from park hopping, or even going to a different park for dinner, etc. Lots of people do it. Just leave yourself plenty of time.
Also, there is no resort to resort bus transportation. To go from CSR to another resort for dinner you would have to take a bus to a park or TTC, and then take a bus/boat/monorail to the resort you want to eat at. Many resorts have great restaurants, so it may be worth doing. Many people rave about Boma and Jiko at AKL, Artist Point at WL, 'Ohana at Poly, Chef Mickey's at CR, etc. They are also lovely resorts to look at.
If you're there long enough you might want to spend a pm resort hopping. It's a chance to rest from the hectic pace in the parks and it can be fun. You can check out places to stay on future trips. By the way, the Poly, Grand Floridian and Contemporary can all be reached by monorail. Once you are at either MK or TTC it is easy to hop the resort monorail and see those three. Also, the Epcot resorts (YC, BC, S/D, BI) are all within walking distance, although it's a long walk.