I used to live in San Diego, and now I live in Santa Fe, so I thought I'd respond briefly...

I think the weather might be warmer (but may be foggy) in San Diego in early April than in New Mexico, although the southern part of the state should be warming up nicely by then. If either place gets any good late winter precipitation (we're still waiting for it here) you could luck out with desert wilflowers. In terms of botanical interest in New Mexico, I think the southern part of the state is better, the cacti, yuccas, agaves, ocotillos, etc. of the Chihuahuan Desert region are pretty neat and some might be flowering by April. Of course, the two best aspects of New Mexico are the cultural heritage (Ancient ruins of Bandelier and Chaco Canyon highly recommended, as well as modern day pueblos and Santa Fe culture) and the geology (lots of red rock, old volcanoes, canyons, and mountains to explore).

A word on Southern California: if you can get away from the urban sprawl, there are limitless possibilities for sightseeing in a relatively confined area. A few favorites of mine include La Jolla and Torrey Pines just north of San Diego, Anza Borrego Desert State Park, San Jacinto/Santa Rosa Mountains National Monument, and (a bit farther away) Joshua Tree National Monument. The latter three have some incredible native Fan Palm groves which are really impressive to visit. Just about everywhere in California you can find amazing endemic plant species, after all, its one of the world's richest regions for plant biodiversity.

Wherever you go, enjoy

Thanks so much, Chris... Santa Fe is one of the places that rose higher on our list today, so your response was just what was needed! We're having trouble deciding what to do but I think we've narrowed it to San Diego or Santa Fe.

Flying into ABQ is much cheaper than Santa Fe -- what's the drive like from there?

Thanks again for your help!

Yes, the Santa Fe airport is pretty much out of the question these days (I guess it's tiny and caters mostly to small private airplanes), but the drive from Albuquerque to Santa Fe is only about an hour, interstate all the way.

Have fun planning...

Check out the drought situation in NM. I was just in SE Arizona, and it's dry as a bone with no flowers. You might want to postpone that part of the country till a wet winter brings nice scenery (taking for granted you are a nature lover).