We are traveling to New Mexico next August and are planning on visiting Albuquerque, Santa Fe and Taos. How many days would you suggest for each? Is Carlsbad worth visiting also?

Carlsbad is worth visiting but not at this time as it is a long way from the other places you want to see. I would suggest you go to Bandelier NM when you are in the Santa Fe area, it is not too far from there. How long you need in each place depends on what you want to do. Hiking? Museums? Shopping? History? Native American sites? A little more information would be helpful.

We visited New Mexico a few years back. We spent 2 days/nights each, in Albuquerque, Taos and Santa Fe - which worked out perfect for us. A nice combination of museums, day trips and activities. Here's what we did: (taken from what I posted back then...)
"...Flew into Albuquerque, settled in, walked around the Old Town, and stopped in at the small but interesting Rattlesnake Museum. Next morning saw the Albuquerque Museum of Art and History, then drove up to Taos(2.5 hours)for 2 nights. Visited the Martinez Hacienda and Governor Bent House. Next day visited Taos Pueblo and went rafting down the Orilla Verde - the really mellow part of the Rio Grande River(mellow - until we got caught in a thunderstorm!)
Next morning on to Santa Fe(a 90 minute drive) for 2 nights. Explored the Old Town, and toured the Museum of Internatinal Folk Art and the Museum of Indian Culture and Art - both located on the appropriately named "Museum Hill" area. The next morning we headed out to Bandelier National Monument(a little bit under an hour from Santa Fe)to see the ancient cliff dwellings, and finished up the day seeing the Palace of the Governors and Museum of Fine Arts - both on the main plaza. We drove the Turquoise Trail(NM 14)from Santa Fe to Albuquerque, stopping along the way at Madrid(where there is a "fake" diner built for the "Wild Hogs" movie, filmed there last year)to see the Old Mining Museum, and lunch at the Mine Shaft Tavern.
About 20 minutes from Albuquerque we went to the Tinkertown Museum - a very unique place!
Back in Albuquerque for the final 2 nights, we headed out early for the 1 hour drive to Acoma Puelbo(aka: Sky City), then onto the Balloon Museum later in the day, and we ended our tour of New Mexico with spectacular views aboard the Sandi Peak Tramway..."
Hope this helps!

We are interested in hiking, museums, history, photography and eating. Thanks for the comments so far. Very helpful.

I am local and would love to help you. I am on vacation right now, but will get back to you next week.

We did a similar 7 day trip in Dec/Jan 10. Spent 3 days in SF, 2 days each in Taos and Albuquerque. I would have liked to spend more time in Santa Fe if I had to do it over.