I've noticed a few people ask how to disable 3G and just use 1x for data, and since it's not in the mobile network settings menu people started to assume it wasn't there.
If you open the Phone app and dial
it will automatically bring you to a menu, click on Phone Information, scroll down to where you see "CDMA auto (PRL)" change this to "CDMA only", and your phone will stop using 3G and the status bar will confirm this.
This will decrease your network speed, but apparently increase battery life. Also it will prevent roaming charges if you don't have a national plan (from what i hear?)