My iphone 5 keeps telling me "unable to join network" im at a hotel & sum of my friends with iphones are connected.. what do i do??

It may actually be the problem from the hotel side.

Still, you may try these steps, this won't delete any data from your phone.

Settings - General - Reset - Reset Network Settings

Try to reset your device.

• Press and hold the Sleep/Wake button
• Press and hold on the Home button
• Keep holding both buttons until the display turns off and back on with Apple logo on it.

Alternatively, you may go to Settings - General - Reset - Reset All Settings

https://support.apple.com/en-us/HT201559