I would completely skip on Solavei and stick to Spot Mobile or Simple Mobile. Customer service has been a touch better with Spot, but Simple has a bit more flexibility in plans.
Spot offers Unlimited Talk, Text and Data with 3 different offerings - $39.99 gets you 500MB @ 4G - $49.99 gets you 1GB @ 4G - $59.99 gets you 2GB @ 4G... All these include free international calling credits and unlimited 2G after your limit is reached. Spot plans are purchased over the internet so there are no taxes or fees.
Simple offers the same with 3 different offerings as well - $40 for 500MB, $50 for 2.5GB and $60 for 4GB... No taxes or fees as well.
Solavei offers 4GB of data for "$49" plus up to 24% taxes. They charge you a post paid tax setup while marketing as a 'prepaid' service. It's loaded with billing issues, coverage problems and horrible support (check out
http://support.solavei.com if you want to see some of the stories first hand).
My Solavei bill for the 4 months I spent with them was $59.60 a month. I get better service support from Spot (I use more Wi-Fi so I don't worry about exceeding the $39.99 plan too often) and save $20 a month off the top. Simple would do the same for me as well and their coverage is exactly the same as Spot's.
If you want to try either one,
Discount Cellular from Red Pocket Mobile, Spot Mobile and More! is giving away a free sim with any activation of $29.99 or more. It's pretty much a no risk deal for you. If you email them and ask for a second one to try out first, they might even send you a tosser card and one to port your own number over to Simple.