since you are only needing mobile internet for the five months you are on the road i would suggest you consider upgrading one of your verizon cellphones to a model that can tether -- check out this list of phones and make sure software is available for your operating system:
http://vzam.net
tethering a phone means no long term contract obligation for data service. turn it on and off whenever you need it just by calling verizon.
fyi, on interentbycellphone group on yahoo, there are many fans of the motorola v750 adventure because of its signal reception. i like it because its known to work with cradlepoint routers, so you can share the internet connection from one tethered phone, with more than one computer via wifi. not sure you can still get that phone, but if you have time before you hit the road i would suggest calling several local stores to see if you get lucky and find one? another good option would be the LG Versa or Dare.
one more thing to watch for about phone tethering. some phones now require a data plan... i am not sure if phones i have recommended fall in that category so make sure before you commit to one?
if you do not like the phone tethering idea, you could go get the usb760 with no 2yr contract for $129.99 at bestbuy. in addition to modem cost, you will have to pay $35 activation fee and then $60/mo, but you can just stop service after the five months... not be tied to a 2yr contract.
the usb760 works great with cradlepoint router like the mbr900
hope this helps?