I am looking at buying my first smartphone, probably the Cingular 8525 and I have a few questions.

1) This phone has wifi, is it possible to access the internet using the wifi if you don't have a data plan without racking up additional charges?

2) If you don't have a data plan is it possible to prevent your smartphone from accidentally accessing the internet when not in a wifi hotspot and racking up additional charges (such as disable the 3g/other capabilities)?
Basically, I want a smartphone but would really like to keep my wireless bill in the $50/month range and I would be content with just using the internet capabilities in areas with wifi. I am primarily interested in using it for phone/text messaging/email/slingbox.
Any help would be appreciated, thanks.