If the surface is firm and not too bumpy, it'll work. Smaller and skinnier tires have a poor "cone index", they sink in more on soft surfaces than larger tires, so perform poorly, as others have related.
Be careful hosing off the bike, try to keep concentrated water stream away from the sides of the rear hub, to prevent water intrusion. A local bike shop that specializes in Internal Gear Hubs like the Brompton, recommend additional lube from new, using marine wheel bearing grease for the outer bearings, both as a barrier against water getting in, and keeping liquid gear lube inside. They also recommend an annual teardown and lube, if you ride in rain (or perhaps also frequently hose off), to prevent permanent damage to the hub internals.