You can get WiFi amplifier antennas to help improve the signal. For example at one RV Resort we went from a 2 bar signal to a 5 bar signal using a USB connected WiFi antenna I got at Best Buy for $49.00. It also picked up a couple of additional WiFi sources that were outside of the campground.
Another option is to load movies onto an external hard drive while you are at a location with good WiFi service to watch at a later date. You'll need to get a software that provides the ability to transfer or convert from DVD or Streaming source to the external hard drive.