Not sure about the width, but I think there's a minimum tyre width that each wheel can handle. The rim sticker should have some info on that.
Slicks will tend to puncture easier than MTB tyres will, so be sure to have spare tubes ready. One way I learned to prevent punctures is to keep the pressures really high, anything above 65 psi for me, even though the max tyre pressure saz 65 psi. I run mine about 70-80 psi.
I run Performance 26x1.50 tyres. At $10/each, they're ok, and much more comfortable than knobbies on the road.
