Ok I am far from being a tech but things I would do

Shut it down..take out the battery reboot

Turn off the fire wall (just to check)

are you sure its free? some shops make you at least buy something there and then you have to register and get a password

when the last time your sister used it? Are you up to date on your service package?

Try another location

last resort..Sit at a table by a window wrap a metal coat hanger in tin foil and tape it to table making sure the hanger is a long as you can make it pointing the hanger east. stick one hand in side your neighbors large Mcdee's coke and put your foot on the chair leg across from you all the while sucking down a milk shake. If this doesn't work I am sure that someone will ask you if you need help...you might even get a ride to a place with great wyfy service .....trust me!