My Dell Latitude XP laptop got knocked to the floor. It fell on the side where usb port was connected to printer. Usb port pins are now bent and port is unusable. Dell said I have to replace motherboard! Is this the only way?

It depends. If i am understanding you correctly the problem is that the usb port has broken loose from its connection to the mother board.

can you boot the machine (ie everything else works but the usb)?
Check for a docking connector (usually on the bottom, or dead center on the back). Check dells site for what docking stations are compatable and connect the laptop to the dock then use the usb ports on the dock (skips around the onboard port)

if your feeling a bit more ambitious you could try plan b
This should be solved by 1) disassembling the laptop (so you can access both sides of the mother board) 2) inspect the damaged connection (are the pins broken off or just loose from the solder pads). 3) if the pins are intact, then you should be able to gently bend them back and re-solder them into place, if the pins are beyond help then you would need to remove the old one (use a braid or a ****** to get the old solder out) then plug in the new one and solder it up.

I will point out that you need to be relativly proficient with your soldering tools before bringing them anywhere near the mother board of your pc.

No, it's not the only way, if you have an unused PCMCIA port in your notebook. The width of the PCMCIA port is about the height of a credit-card, and the height of that port is about the thickness of a few credit-cards.

Purchase a PCMCIA adapter that has two or three USB ports.
Insert the PCMCIA adapter into the slot,
and connect your USB device to one of the USB ports.