bballdad - Last year was the first time that I went. I only hung out at the Padres/Mariners complex in Peoria. Its nice, real nice. No trouble getting tickets whatsoever even as a walkup. Stadium comes close to filling up, but there are regular seats as well as lawn seats in the outfield. All nice. Bring sunscreen!
I've heard that the new Dodgers park at Glendale is very, very nice. At other times I've also been to the Giants stadium (Scottsdale), Angels (Tempe) and the Royals/Rangers (Surprise). All nice.
Diamondbacks and Rockies train in Tucson...not really worth the drive (2 hours) unless you wanna continue on to Tombstone or Mexico for some old West sightseeing. Both of those teams come to the Phoenix area for games.
Next year (if I go) I hope to go to the Reds/Indians site (Goodyear)...first year there for the Reds.
Best hotel reservations can be found earlier. But there's enough rooms to get one fairly late as well.
Enjoy!