Re: Data package renewal with different package, rollover?
You can buy a new data package when you deplete the current one - no need to wait for the original package's expiration date. And you'll get a new 30 day period with the purchase of the new data package.
At&t's legend on the coverage viewer re: 3G service is ambiguous - but I believe their areas marked as requiring a 3G device may just mean that they don't have 2G service in those particular areas. (I've never seen clarification by at&t, but have seen a number of posts out here that seem to support that interpretation.) I don't believe their intent is to imply the opposite - that those are the only areas where they have 3G coverage for prepaid service, so many areas of the west coast should receive 3G service on a prepaid basis. (I myself get 3G service with my prepaid plan and I'm not in an area where at&t indicates a 3G device is necessary.)
It's more clear if you look at the data tab and drill down at least one step so you can see details with the expanded legend by coverage "type" - this is for post paid service; however, the only areas where at&t's prepaid customers don't have access to the network is in partner coverage areas. So presumably you wouldn't have coverage at all on a prepaid plan in areas marked as "partner edge" or 'partner gprs" (or "no service"), but you should get 3G coverage in the "mobile broadband" or "4G" areas as long as you have a 3G capable device.
=^..^= There must be a happy medium somewhere between being totally informed and blissfully unaware.