Most hotels have to have atleast one person over the age of 21 to check in. Past that it shouldn't matter that you're under 18.
Certainly, as long as you do not violate the hotel's use policy and the rules associated with your conference room rental. Some have a policy that any alcohol must be served by hotel staff, but check your agreement.
check party city or other party stores. also, you can check online or on Halloween costume places.
maybe at a hotel
It depends. Check with the management and let them know what you are planning. If you are planning to party like a rock star, no. By RavennaB, It's no allowed, it will influence the others guests.
In regards to check cashing, a single or one party check is a check in which the check writer and beneficiary are the same person. In other words, if I write a check from my bank account to myself, I am writing a single party check. Contrast this with a two party check in which one person or company writes a check to a second person or company, or a three party check in which one person or company writes a check to a second person or company and a third party guarantees some part of the check (usually the funds).
A "second party check" is a check where the payee is depositing or cashing the check. For example, Bob Smith writes a check to his brother John Smith. John Smith is the payee, (second party) who deposits the check into an account in his own name, or cashes the check. If John Smith wants to endorse the check on the back to a different person, that other person would be a third party. The check would now be a "third party check." Banks are likely to not accept this type of check if the third party tried to cash it, because they cannot verify endorsements.
at a hotel lobby
they made a big party and invited everyone.
in the port hotel
A two party check is a check which is made out to more than one party. To cash or deposit a two party check, the check must be endorsed by both partied that the check is written out to.
You throw your own party.
a party where everyone wears costumes