You shouldn't be worried at all.
You should enable 128-bit
WEP on any reasonably-recent WAP (Wireless Access Point) and not worry. 8)
By "reasonably recent", I mean "recent enough to support
TKIP."
If you are the more worrysome sort, you can also enable
MAC Address Filtering.
This is the state of the art today, and provides adequate security in most cases.
Everything will change when
802.11i becomes generally available. 802.11i is
really secure.