Typical town guardsman?
2nd Level Warrior for most places, a professional and modestly experienced combatant used to low-end engagements with drunks, pickpockets and other low end encounters but not trained or experienced in dealing with powerful dedicated menaces like big monsters. Novice guards or guards in particularly peaceful towns where nothing ever happens might be 1st level warriors, guards in frontier towns where they have to defend themselves from marauders/monsters more often or rough & tumble cities might be 3rd level warriors on average.
While a typical PC can mop the floor with them, a patrol of 2 or 3 2nd or 3rd level warriors with what I'd consider typical guard equipment like chain mail, light crossbow, shortsword and a light shield, and of course some manacles (maybe even masterwork equipment depending on how rich the town is) would be just fine for dealing with typical drunken barfights between Commoner 1's using their fists, daggers or improvised weapons (or even things a little tougher), and other low-end encounters they'll likely find in town. They might not last long in a dungeon or in the deep wilderness, but this is the (relative) safety of town.
I'm definitely for more of the "what is there, is there" idea, and I'm not about to automagically level up all the town guards or quadruple their numbers to make a tough fight scene. Just because a party 10th level PC's cheese off the Magistrate of the Town of Bilgewater and all 12 town guards suddenly jump up several levels or get PC classes or somehow get huge reinforcements. Rewriting the game world to constantly be a perfect challenge for the PC's is a huge stretch of suspension of disbelief. That sure would make my PC's scratch their head in wonder about why the town needs them go slay the dragon that is threatening them, when they've got an entire garrison of guards that is as strong as they are.