No WiFi signal in RV Park--can I boost it?

Try an external ?directional? antenna, (like the Hawking HAI15SC Hi-Gain antenna with a 2dBi to 15dBi boost), the steel in your trailer can interfere with the WiFi signal reception under some conditions in ?fringe? locations. Another option could be (if you have the $$ and the park management is willing maybe to even pay part or most of the cost) to get them to install a ?range-extender? access point router (and you could get the compatible receiver) which would give you a better chance of signal reception over distance. Something like the Hawking Wireless Access Point and Hi-Gain Signal Booster Kit, which can boost the power output to 500mW (standard average is 90mW). I?m sure other manufactures have comparable ?booster? equipment, you would need to take a look at what is available to you.

Take a piece of aluminum foil (about 8" square) put it about 2" behind the antenna so it directs to the transmitter ( |- X )
|=foil -=receiver antenna X=transmitter
if you get a better signal and can connect, a high gain antenna is all you need, if you just get a better signal a directional antenna (best would be outside on a pole a little higher then the surrounding trailers) be careful not to get too directional the higher directional the harder it will be to "point" at the signal.
you will see ratings like 180 degree or 30 degree this tells you how much direction it points remember geometry 180 is half a circle the narrower the "beam" the longer the range but the better you have to "point" it.
if you don't get a better signal a repeater or more power at the source is needed

If the free broadband WiFi is a service that was both a selling point in attracting tenants, and of course part of your rent, then the management has a duty to make sure that everyone is within range of their signal, (and should take into account all the locations in the park as well as the possibility of steel as the building material).

If they are not willing/able to do anything, there are free plans on the internet for building your own directional antenna, including one using a Pringles can, and one that gives a template for the proper arc to unfold a tin can to use as a parabolic antenna, including the focal point where the USB antenna is placed.