If you are interested in going to Mexico, a few places come to mind - Verana (very upscale casitas in the jungle) or Majahuitas (think Robinson Crusoe/deserted beach but all the amenities you would need). Both are a short boatride from Puerto Vallarta.

I just received an announcement for a new place in the Sierras, a hike-in lodge with "luxury" tent cabins. Hot showers, all meals provided, for $225 per person/day.
www.SequoiaHighSierraCamp.com

i second el capitan canyon near santa barbara... my husband and i were looking for the same thing you are, and we had a great time there a few months ago. we loved staying in a wooded area that was so very close to the beach as well. also loved the creek running through the canyon. we even borrowed some of their cruiser bikes - for free - and rode up and down the trails along the ocean one day. so fun! i appreciated that the cabins were well spread out and that cars were not parked all around all the time - you drop your things off and then go park in another area. the cabins were quite comfortable with gas fireplaces and jacuzzi bathtubs, and the proximity to the wine region (santa ynez and los olivos, the whole "sideways" deal, and solvang) was lovely - plenty of nice restaurants around there, and wine tasting a-plenty. we never went into santa barbara for anything, but you definitely could... i would highly recommend this place. as a side note, a friend of mine recommended the cloud climber jeep wine escort service (you don't really want to taste and drive) - we are not the guided tour sort, but we really want to do that next time we go.

I just read about this one this weekend:
http://www.sequoiahighsierracamp.com/

Looks pretty nice.