I may be wrong but I think you had mentioned being close to Camp David. Take a look at the coverage map for MetroPCS / Tmobile. Around Haggerstown and such, there is 4g coverage. Further out, not so much. If you are lucky and can get a 4g signal, they do offer true unlimited plans. The speed isn't amazing but I usually get around 5Mbps or so down here in the Tampa area. Even on the plans with a bandwidth limit, they just slow you down to about 112Kbps instead of raping you with overage charges.
You may have already checked with them though and are probably in a 2g coverage area.