Out of curiosity why do you want to have access to the GLONASS satellites?
Unless your having several problems making contact with the GPS satellites I don't really see a point. Both systems work well enough to provide accurate locations...
While both are open to the public the only devices I have seen natively connect to GLONASS over GPS have been from Eastern Europe (which makes sense) and a few Middle Eastern devices, while the rest of the majority of the planet uses GPS.
Also, as for what @andrewdroid
stated above that very well be a possibility, depending on what app your using for navigating.
Actually, looks like that's the case... http://www.qualcomm.com/media/blog/2...ion-your-phone
it's from 2011 (and refers to the S2) but our processor should do the exact same thing. There might be something in the kernel that would let you choose a preference but since your on AT&T with a locked bootloader I don't foresee you using a custom kernel unless your on a older Loki-susceptible baseband.