Yes just go with the lower plan. I was able to access my school's Exchange account for e-mail just fine on my Droid Eris with the lower plan, so I don't see why you couldn't do the same with the DX.
Try putting the Mobile Network widget on the home screen for easy access, and it should allow you to toggle Mobile Network on/off. Sorry, I don't have a DX, but that's what I did on my Eris. Hope this helps.
I only had accurate signal strength on my Eris after I loaded a ROM. Without it, I had 0-1 bar where I have 4-5 bars with my Storm. My Eris had -80dBm most of the time. It was a bit annoying, but as long as you can browse the web then you're set!
Evil Eris 3 for me, but it really is up to you. If you start liking a ROM just make a nandroid back up and try as many ROMs as your heart desires. If you don't like what you see in the other ROMs just restore your back up and your ready to go.
I suggest backing up everything and doing a factory reset and see if that resolves the issue. If this Eris update really comes out on the 16th, then it might resolve your issue. It's your call; just my 2 cents.
Item Description : 1 Rooted HTC Droid Eris
Price : $125
Condition : 9.5/10 - I gave it .5 lower from 10 because the device itself is in perfect condition but there is about 2 cm of the rubber surrounding the charger cable that has slid further down the wire exposing a tiny amount of wire...
I will use the free and open-source "Kick iPhone Butt" widget, only available on the new Sense-UI, to make all iPhone owners my minions in my plan to help Android / Google take over the world! Muwhahahaha!!!
I have an HTC Droid Eris, but I would like to get my mom an AWESOME Mother's Day present to replace her buggy Samsung Glyde or give it to my dad, who is using a Samsung Knack, so he doesn't have to get an iPad.