Maybe a dumb question (or two)

[pll]

He also said that with the smaller tire I would be more likely to have flats riding on the road (as opposed to the rails-to-trails bike path)

Tsk, tsk, bad bike shop guy. I have 23s (cheap stock tires, Continental Sport 1000) and I have used them for 7 years (2600 miles on my current odometer). I have yet to have a flat. I am religious about ensuring they are properly inflated prior to every ride, and I have taken these tires through roads and sometimes gravel trails.