That'll output any serial data that gets received, regardless of whether it's GPS or not.
The Adafruit page says:
The LED blinks at about 1Hz while it's searching for satellites and blinks once every 15 seconds when a fix is found to conserve power.
So at 1 per second it hasn't actually got a fix yet - it flashes every 15 secs when it's got a fix. That could actually be why you're not getting any data out - maybe you just need to wait a bit longer :)
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It should work, and the software looks fine...
How have you wired it? Generally TX connects to RX and vice-versa for serial.
To debug, you could do just the following:
That'll output any serial data that gets received, regardless of whether it's GPS or not.
The Adafruit page says:
So at 1 per second it hasn't actually got a fix yet - it flashes every 15 secs when it's got a fix. That could actually be why you're not getting any data out - maybe you just need to wait a bit longer :)