I am wondering if I have a BlackBerry with Wi-Fi on BES can I use the Wi-Fi connection to connect to the BES for e-mails, BB messenger, and all the other features? Right now I get a very poor signal at home so I want to be sure that if I get a device with Wi-Fi that I can turn off the mobile network part and use Wi-Fi only and still utilize all of the blackberry features other than the phone. We currently do not have a policy in place on the BES other than the default policy.
Thanks

The 8310 (which is in your profile) does not have WiFi capabilities.

Assuming your profile is wrong, or you get another device, yes you can do that, I do it all the time.

Yes I know the 8310 does not have WiFi. I am about to activate the 8900 and was curious if I would be able to do that.

8900 has Wi-Fi.

Yes,
The 8900 has wifi and will work for exactly what you're looking for.

Also, depending on what network you're on, it will work for phone calls and sms as well!

That's correct - in the US, if you have T-Mobile, your calls (and data) will work over WiFi. With AT&T, your data will work over WiFi (but not your calls).