Anne_ST: Don't worry about it anymore.
To all: I was fortunate enough to reach a capable-minded support representative on the phone. Long story short:
ANY PHONE YOU WISH TO USE ON STRAIGHT TALK MUST BE COMPATIBLE AT 850MHz AND 1900MHz.
ADDITIONALLY, KEEP IN MIND THAT PHONES HAVE SEPARATE SPECIFICATIONS FOR 2G AND 3G NETWORK CONNECTIVITY. For example, the iPhone 3GS does UMTS 850 / 1900 / 2100 for 3G connectivity. The Galaxy Mini does UMTS 900 / 2100.
This is NOT compatible with Straight Talk service for 3G connectivity so you WILL always only get an EDGE connection on this phone with Straight Talk. Period.
iPhone 3GS specifications: http://www.gsmarena.com/apple_iphone_3gs-2826.php
Samsung Galaxy Mini S5570 specifications: http://www.gsmarena.com/samsung_galaxy_ ... 0-3725.php