As soon as we got out of the sawngthaew, a man in a pickup truck called out “madame, madame, all day tour.” Mom and I said “yes” and “no” at the same time. My gut instinct here is to say no to the first person who offers you anything—or at least the first price they offer. But mom thought it would be easier to get a guide immediately instead of hitch-hiking to the visitors center (the normal way of getting there from the gate). It wasn’t terribly expensive and we had a good time, so no harm done.
(We probably could have gotten one cheaper though!)