FreeBSD router two DSL connections

[James Long]

This is for an internet cafe, right?  Not a mission-critical system?
Yes, I realize your mission is providing internet, but....

Buy two DSL feeds, and two WAPs.  Put one WAP on each feed.
Set them to different SSIDs and different RF channels.

Then the wi-fi clients will associate with one or the other, hopefully
on a 50/50 basis, or perhaps geographically distributed in proportion
to how far (or how line-of-sight) they are from either WAP.

If one WAP fails, odds are good that clients will still be in radio 
range of the other.

So there you go, redundant fail-over in case one feed goes down.
For a $1.75 cup of Americano, that's about the most your customers
will have reason to expect.