Perhaps one of the best things of having a downtown ballpark is the number of pubs, eateries, bars, and restaurants that fans can stop by before a game for an adult beverage and/or bite to eat. Mission Bay certainly has a large portfolio of establishments, but for me, hands down ... it's Pete's Tavern on 128 King Street, right across the ballpark. Pete's certainly has a large selection of draft beers, hearty bar menu, great setup of the bar (i.e. flatscreens, chairs, stools, loft, etc) ... but the location and bar staff are what makes it great. It certainly will get crowded on gameday, but that's part of the ambience of Pete's - everyone wants to be there.
Now, every now and then, you gotta have a backup establishment, and that too is right next door at Pedro's Cantina. Pedro's opened this past summer and it's been a hit since the day it opened. I'm guessing it's at least 3x as big than Pete's, and the food is awesome ... in fact, I'll stop by Pedro's first for one of their signature burritos and then head over to Pete's! Honestly, you can do that, and they're cool with it. So much so, that you can walk between those two establishments without ever going outside.
Okay, so you read mine, where is your pre-game spot?