Make ABSOLUTELY sure that it is a crib. Plenty hotels will tell you that it is a crib, but it really is a a pack-n-play. Ask if it is wood or metal, the metal ones are generally not the most pleasant cribs. Ask if the mattress is a full thickness (5 inch) not the thinner one (3 inches). Most hotels use the thin mattresses and they just are not very comfortable. Also be aware of hotels using ADULT-SIZED sheets for the cribs. This is extremely unsafe, and should be avoided as it poses a strangulation hazard for babies. If they do not offer crib sheets, it is unsafe to use that crib!
Make sure always to bring two fitting sheets on your vacation and avoid surprises.