We have the Cricket unlimited plan on one phone and IF we we exceed 22 gigs and are on a congested tower, it can slow down. How slow? I have no idea.
The other Cricket phone and a T-Mobile hotspot both have unlimited 128k after they hit their allotments. I purposely hit it to see how bad it was and 128k is good for web browsing, emails and even streaming music. If that's all you need, you can get it for $6 a month on TMO.
I wish I got a better TMO and Sprint signal. The $35 TMO unlimited is half what we pay for Cricket. Then again I guess we are paying for that AT&T coverage both here at the house and everywhere else.