27 will do but it's pretty skinny. It will be easier to pinch flat so you have to run more air pressure, thus making a harsher ride. Also makes it easier to wash out on gravel. It will be nice and fast on hardpacked dirt or pavement though.
Also making it difficult is the fact that everyone's measurements are different. Michelin's 30c is about the same as other 35c, for example.

Ideally, you want something that can clear up to 35c tires. That gives you the flexibility to try different tires for different conditions or riding preferences.