I have zero latency problems with the M-Audio Delta 1010 Interface, but that's plugged directly into a PCI port on the Motherboard of the computer and it's pretty expensive. And you'd need more equipment to use that.
Unless you're using Firewire 800, it's a very common misconception that Firewire is faster than USB 2.0, but it's not. Firewire has a maximum sustained throughput of 400mbps and USB 2.0 is 480mbps. Of course, all of those speeds are quoted as "theoretical" by the various manufacturers.
M-Audio is a good solid manufacturer to go with if you're looking for a recording interface for the guitar or any other instruments. I know at least two people who have purchased the M-Audio Fast Track
and have been very happy with the results. And it comes with multi-track recording software too. Not bad for $119.00