Anthony has pointed out a thread on the Capcom Unity Forums with English players Playing Monster Hunter Frontier.
A group has very recently revealed on capcom unitys forums that there
is a way to play frontier in the united states without getting banned
or breaking any laws. the game is pay to play at around $15 a month
and is in chinese, but its an easy solution and one that anyone can do
with no true problmes. this link to the forum has instructions on how
to get on how to pay and even knoledge of an english speaking guild.
Its not an english version of the game, but for the first real time
americans get to enjoy the monster hunter goodnes they want. as a note
the game is alittle behind on updates, and is in forward 1 (japan
being in forward 3) and forward 2 is expected some time next year
The thread is a little old at this point, but You can check it out here