For us it has been the secure VERIZON MIFI plan... We would not be happy with the WIFI connections all around that are not SECURE. We are grandfathered in with a 3GB DATAPLAN for $27.  I think their current 5GB Dataplan is $60.   If you plan on downstreaming TV then the MILLENICOM MIFI network has a 20GB dataplan which uses the VERIZON network for around $70-$80 a month...
The 3GB monthly dataplan is perfect for us checking-in with the kids, paying some bills on-line and minor surfing of the internet...
Roy Ken