We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Peter Scott saying something like:
No good. That only handles 900MHz, UMTS/3G is close to 2.4ishGHz. Google it and you'll find out more.
You don't actually need an amplifier, just a good UMTS antenna of at least 9dBi (preferably 12 or so) and a good quality downlead and pigtail to enter your card or dongle.