Actually, my husband hails from Covina, and he has tons of family out there, so we do get out there every so often. Usually every second of our time is spent visiting relatives, though. I have to get down on my knees and beg just for part of a day to visit Disney or the San Diego Zoo.
The last time we went out West we went camping and hiking in several National Parks:
Bryce Canyon
Cedar Breaks
Zion Canyon
Arches
Canyonlands
Colorado National Monument
Rocky Mountain
we also camped for a couple of days in Glenwood Canyon right on the banks of the Colorado River, and let the kids swim in one the largest hot springs fed swimming pools in the world in Glenwood Springs.
We also spent a bit of time in Denver and Omaha.

That was a great trip!!
This summer we'll be going to a high school graduation party for my husband's nephew in Minnesota and then will go out to the Black Hills to go hiking and camping. We plan on hitting:
Badlands National Park
Wind Cave National Park
Jewel Cave National Monument
Mt. Rushmore
Custer State Park to visit the wild bison and burros
The Wild Horse Sanctuary in Hot Springs
the hot springs swimming pool in Hot Springs
Hopefully we'll have a great time on this trip, too!