If you have a Type II (cardbus) slot, you should get USB2 speeds. Check your
manual, or your manufacturer's website to find out, if you don't already
know.
USB2 is only available on Cardbus cards (almost the same form factor but
different interface). If your PCMCIA slot accepts Cardbus cards then this
will be the only route to using USB2. If your slot does not accept cardbus
cards, then you are somewhat stuffed.