Where I go depends on what I want to do, if you want to catch the most fish you can go as far north or as far up the San Juan as you have gas for. The closer you get to a river intake, the more fertile the water is and that means more and bigger fish. That being said, you can catch 100 fish a day just about any where on the lake if you know what you are doing and are there at the right time. If I'm wanting to take people that have never seen the lake, and I really want to impress them, I camp some where in between the mouth of the Escalante (MM 68) and the mouth of the San Juan (MM58). Spend one day and hit every canyon in the Escalante arm. There are many arches alcoves and spectacular rock formations that are breathtaking. If you do much hiking and climbing up into some of the big alcoves this will take two days. Spend another day hitting most of the canyons between MM 68 and the canyon that Rain bow bridge is in, can't think of the name of that canyon right now, but some one will read this and let you know. There are some really spectacular winding canyons in this area also. Take a day and see rain bow bridge then go down to Dangling rope marina to refuel and get some ice cream. Go up the San Juan one day to look and fish, Go up to Neskahi and fish from there up to the great bend. Stay mostly on the east side. If you can't catch fish up there you should consider a different way to spend your spare time. Fish early and late for bass on rocky shorelines and points. Always have a couple poles ready for striper boils, they can pop up any where at any time. Read other fishing post on this site for ideas on baits to use. Keep in mind that it will take you 7 to 8 hours to get there from Page and 4 to 5 hours to get there from Bull Frog in a house boat.
I have traveled all over the world, and Lake Powell is still my favorite place to spend time. Guarantee that you will be planning your next trip before you leave.