As mentioned, the Moab area can be very crowded this time of year, especially around the Easter Jeep safari. Weekends are the worst. Zion is doing public hearings on how to limit or ration visitation as it's getting crowded most of the year now. You also have the off ATV rallies, off road rock crawling events etc starting around that area in March. It's getting crowded because it's one of the best times to visit. I would get reservations around any of the national parks for sure, state parks too if you want to be there on weekends.