We were there 3/14-3/21 this year, and DH went to two Braves games. Tickets were about $22, plus those stupid Ticketmaster fees. As far as were were able to find out, tix are only available through Ticketmaster - there isn't a general box office at WWoS.
He really enjoyed it - liked the facility, etc. The week we were there they only played one night game (7pm) so we ordered that ticket in advance because they seemed to be going faster than the daily 1pm games (based on "best available" on the TM site); he knew he'd probably do another but didn't want to be locked in. He ended up going to a day game on Saturday which was sold out when he got there but he bought a scalped ticket for $25 easily.
I know people complain about March crowds, but honestly, we didn't think it was bad at all. We have a DD3, so we're early-ish risers anyway, so we just did what lots here recommend - hit a park at opening, stay4 hours or so, head back to the hotel for a leisurely nap/swim break, then return to a different park for the late afternoon/evening. Doing it this way we never waited more than 15 minutes or so in line, and then only once or twice, and maybe once DH skipped a ride because of the line (he's more into the big/fast stuff that DD couldn't/wouldn't do).
THe whole trip was great, and I know he really enjoyed seeing the games he did - a nice break from the parks for him, some downtime for me and DD. I would only avoid the weeks before and after Easter, crowd-wise, but next year that shouldn't be a problem - I'm pretty sure Easter falls in mid-April so spring training will be over anyway.
Good luck planning!
AV