poor 3G signals could give you much faster connectivity that very strong 2G
Go to Phone and type *#*#4636#*#*
It will open the Android testing menu.
There you have several category of information. Tap in phone information.
Scroll down there and you can find set preferred network type.
Set it to WCDMA only, same as in HSDPA USB modem.
Now your phone is in force 3G mode. It will never switch to 2G.
But Remember, in a situation where you don’t have 3G signals at all, you will be totally cut off from data networks