protip about stealth and disguise: Even if you roll high, if you encounter a lot of people, eventually one of them will have ranks in perception and roll high enough to at least chat you up curiously. The world is filled with 80% lvl 1 commoners,  10% lvl 1-2 specialists, another 5% 1-3 lvl warrior/fighter/etc guard types, and then the last 5% has folks with multiple class levels of various things. The pc's are unlikely to run into something exceeding them in level(Less so as they slowly level up) while just wandering the streets, but it's not completely impossible.