Hi Camolas,
about the signal coverage, what you think about to use:
AT+CSQ

it should tell you how good is the signal.
In the modem I have it say that
0 - 9 = very poor or not enough
10 - 15 = good
16 - 31 = very good

May this help you.
If you get your code even good for signal coverage, do you like to share it?