I went! Thank you to everyone who gave advice. It turned out I really didn't need to worry. There were lots of people (I'm terrible at estimating but between 100 and 300 people?) and we blocked traffic downtown for about 2 hours (and apparently caused massive gridlock during rush hour), first from a gathering where people talked and then by marching and chanting. The police were there blocking off the intersections we were in, but no one escalated anything at all. It was simultaneously more exciting but way less emotional than I thought. I thought I was going to cry because I cried at the videos of other people protesting, but everyone was quite cheerful (and the awkwardness of the chants dying out/the people at the open mics saying insane things about how fluoride is poisoning us breaks the tension in real life). The coolest part was having people come out of their homes and businesses to chant with us while we walked by, or the people stuck in traffic who honked in solidarity. So my new advice to anyone who wants to go to a protest but is intimidated is just do it! But maybe get there early so you don't get stuck in traffic trying to get there. And if you live in cold places then the part where you're standing around is really cold (but I warmed up when we started marching).
There's a protest for Eric Garner tomorrow I want to go to. I have never been to a real protest before and I have no idea what I'm doing. I have an address and a time (and now a facebook event without much info). Do I just show up? Where do I park? What should I wear/bring? The Mike Brown protests were peaceful in this city, but it's in New York State, so things might be more keyed up this time. I'll put the city it's in in the comments if anyone else is going and can be my "don't you dare chicken out" buddy.