In reply to snapperdan:
So much depends on the specific route, as well as how much/ where you place gear, that it's hard to generalise.
I've seen people zigzag their way up a short, 'straight' route with careless gear placement. And equally I've seen people protect 'wandering' routes on a single rope with careful extending (and judicious skipping of gear placements).
Pretty much anywhere in the country I'd be happier with two, but if a single was all that was available, it wouldn't put me off. Just choose routes wisely and be prepared to belay a bit more often if necessary.