If you have a good security internet suite - with the anti virus, anti spyware, those usually have built in extra security for networks & wireless.

The router & connection can be set of quite secure too.
passwords and such

If you live in an apartment or close housing it would be more of a concern than if you are in a rural area.

you could test how far your wireless signal goes by taking the laptop outside and with the signal meter showing - walk around till it loses connection.
ours doesn't go very far much outside of our house - and we are out in the country .