In effort to improve the La Fonera signal distance, without having to pop the extra cash for a new antenna (or the overrated La Fontenna), you can make a Parabolic reflector to make the standard La Fonera antenna into a directional antenna.
There are tons of information on this all over the internet. I have tried making a couple of them myself, but really could not test it at long distances (so I really can't tell how it worked). On the other hand this idea is all over the internet and many people have had great success with it. So O encourage you to google the idea and try it for yourself.
Kyros Parabolic Reflector
Fon Boards - "La Fonera signal distance?"
freeantennas.com - windsurfer
El Fon Blog - "Wifi Reflections [1 EDIT]"
TechAnvil - Building A Parabolic WiFi Booster
TechAnvil's design for a Parabolic WiFi reflector