My main question, outside of where else to visit for special beer week events, is should I carry my handgun in downtown Philly?
Philly areas breweries to look for are Sly Fox, Yards and Nodding Head. You might also find Flying Fish (NJ) and some Dogfish Head oddities.
Good web sites:
Mid-Atlantic Brewing News (http://www.brewingnews.com/mid-atlantic/
Philly Beer Week (http://www.phillybeerweek.org/
The touristy areas of Philly are reasonably safe from violent crime, IME, although it's been a few years since I've visited. The hairy areas are/were West and North Philly and that's not where the bars or attractions are. Anyhow, most of the violent crime is between people who know each other, rather than random attacks on visitors.
I'm not a cop or a lawyer, but it just seems like common sense to research the local gun laws; perhaps talk with your department or the Philadelphia PD. Pennsylvania has some weird laws, so there might be oddities about carrying there. Presumably, professional police forums or the NRA web site will give better advice than you'll get here.
Given that you'll be going into bars, stadiums and other private property where they might have restrictions on carrying, my gut instinct is to leave the gun at home. If you "look like a cop" even out of uniform, I can't imagine anyone hassling you. In any case, your most valuable weapons when confronted with most crimes is common sense and a cell phone.