If you're going to go out west, there's a little town in Southern Utah called Kanab. It's amazingly beautiful in it's own right (was where a lot of the classic Western films were shot) but from there it's a short jaunt to Zion Ntl. Park, Bryce Ntl Park, and the north rim of the Grand Canyon. Oh, and Antelope Canyon too... Google it. It's amazing! One of my favorite areas on the planet...
I love Kanab! I spent my spring break there last year volunteering at Best Friends and it's absolutely stunning with lots to do in and around it- and I love all of the places you mentioned. Zion is spectacular. Moab, Utah is on the other side of the state (SE) but also really beautiful, it's where Arches National Park is as well as lots of outdoor activities. I only got to spend a few hours there and want to go back. Mesa Verde in Colorado is beautiful as well.
I lived in Utah for 3 1/2 years and the state as a whole is spectacular. If you head north in the state there aren't the notable national parks, but it's a totally different landscape. Instead of desert you have snow-capped mountains and much more green and the same number of outdoor activities. Bear Lake in Northern Utah is pretty and fun for summer activities- swimming, boating, camping, those types of things and right along the Idaho border- so you can work your way towards Yellowstone and destinations north.
If you're in the NW (which you would be for Forks), Oregon is beautiful. Driving down the coast is really pretty, lots of beach views and wildlife and fun places to stop along the way. Heading inland, Portland and Eugene are both great cities. Portland is great, but I tend to prefer Eugene, it's really quirky. If you just wanted to drive down the west coast the Pacific Coast Highway in California is fun.
Some other places I love in the US are NYC, Washington DC, and Philadelphia (all big cities with big city amenities but also lots of history). I also love Vermont, New Hampshire, and the surrounding area- lots of outdoors stuff, wildlife, and beautiful.
