Relaxing Places in the U.s. to Honeymoon?

My fiance and I are getting married next fall and will be waiting until at least after the holidays to go on our honeymoon. We've decided to do something more lowkey and stay in the U.S. since our wedding is a little pricey. What are some spots you'd recommend? I want somewhere pretty and relaxing. We live in California and want to get out of state, but not necessarily fly across the country. Has anyone been to Montana, Idaho, New Mexico, etc.? Thanks for any tips!