Bruce. the fact that you mentioned the Liam Neeson movie bothers me the most.. let me be clear.. IT was a STUPID movie and the "white slavers" are not hunting tourist girls..

At 18 many kids are travelling on their own. Thats right.. all by themselves or with friends.

They will be fine in hotel.. bored maybe .. but absolutely fine. I personally would suggest you scout out a place for them to eat near hotel. let them have dinner and then retire to room.

They will likely survive the 5 minute walk back to hotel.

PS I have a 17 yr old ( she will be 18 end of May) who is gradding this year too.. I am encouraging her to travel with her friends.

She has considered many places.. I am pushing a bit for Europe because frankly its just safer to me then some of the other places she has suggested.