If you're fat, you're going to hate Avalon. If you have a backpack on, you're going to hate Avalon. Otherwise, you should be able to safely navigate this comically narrow bar and discover its unique place in Lima's otherwise dead nightlife.
Avalon plays real rock music, not Nickelback or Top 40 garbage. Avalon puts a lot of booze in your drink, like so much you'll have to ask for more mixer. Avalon has live shows with no cover with actual bands with original songs, not Lima's usual fair of aging cover bands.
Travis is as friendly a bartender as you'd want, and the hot dogs and beer are cheap.
Just be warned: The place gets crowded in a hurry.