Right, I've not come up against Hodunk myself, so I'll be using the Wiki for the first part. The Hodunks are at the Hodunk Speedway, in The Dust.
As far as I've seen, all bosses respawn, even if they're bosses for a side quest (examples: the Splinter Group, Boll). Verification from elsewhere on Arqade. When they respawn, all of their little friends respawn. So, if there were a bunch of people between you and him, or that hung around him, you'll have to fight them as well (examples: Boom Bewm's Psychos, Flynt's Burning Psychos, Boll's pet Skags).
... Wow, I managed to talk about bosses without spoilers. Awesome.
EDIT: As mentioned in that link to elsewhere on this site, the bosses will only respawn once you complete the mission involving them (namely, get mission, kill boss, turn in mission). So, you can't farm Jimbo until you've completed the mission to kill him at least once.