Ricardo, This is not correct. It will work on other networks. You only need to set-up the iphone and the camera plugged in to do the initial setup (like at home).
Once set-up, you can take your camera anywhere, when you plug it in (power) to the wall, just open your app and change the wifi network to to pulbic (hotel) one, and enter password. Should work fine for your use.
Yes, they can access the feed. It's delayed though, because there not on your wifi. They need to download the app and enter the username and password of your camera. Then they'll have access anytime they want.