There is no way to boost your 3G signal if it's not there in the first place, that I know off.
However, bearing in mind your battery saver post, you could try the following...
Go to phone dial and enter *#*#4636#*#*
this should take you into the "Testing
" menu. Select Phone information and scroll down to "Set preferred network type
" menu which will probably be pre-set to WCDMA preferred
. From the drop down menu, select "GSM auto (PRL)
". This will stop your phone constantly searching for 3G when there is none (or very, very, weak) and help save your battery being consumed by the constant scanning.
Hope this helps.