On well maintained smoothly paved roads, I'd opt for 25's on either a road bike, or a Performance hybrid. OTOH, on a typical mid-western American urban street (a deteriorated thoroughfare), filled with potholes and such, I'd run nothing less than 32mm, on my hybrid (currently running 35's).
A hybrid running 35mm tires within any typical mid-western urban environment should do just fine!
It sounds like your roads are in fairly decent condition. Therefore, I'd possibly even go with 28's. Of course, you have to be mindful of the fact that the less width on the tire, the more observant the cyclists has to be, and the more he has to be attentive to keeping his line.