We visited the Tucson Botanical Gardens today, March 18, 2010. We spent over two hours just wandering around, learning more than we ever thought we would. It is laid out very nicely, and almost all of the plants and cactus have easily readable labels. We did not try the tea house or the restaurant. We had a bit of trouble finding a parking place.
We used our "Tucson Attraction Passport" for 2 for 1 entrance fee, so the admission fee was $7.00. If you're heading to Tucson in 2010, google this attraction discount passport - I think it cost $10 or $15 dollars, but it's well worth it. It has over 50 attractions with discounted tickets or discounted merchandise. We will get our money back several times over while we are here.