If the area you live in isn't well served by Verizon's data network, not much you can do. There is no data signal booster like there is for voice calls. If it won't work well enough, consider returning it for refund.
If you are confident it's not a signal level issue, ask Verizon for a replacement Mifi. My first one kept flashing red when the battery was well charged, while the Mifi was in use. Verizon replaced it and I've had no similar issue with the current unit.
Not sure if it is a coverage issue or a hardware problem. IF I turn it off and back on, the download speed increases about tenfold, but the upload speed seems to still be quite low. It seems to be OK (if you cal640 down and l 30 up OK) for a while then back to very slow up and down.
Last week I wqas getting speeds like 1200 doen and 400 up - today it is like a yoyo.
Does that sound like a coverage issue.