Not sure about Magnolia Beach or Mustang Island, but heard reports on
www.corpusfishing.com/ of plenty of Spanish Mackeral being caught at the Packery Channel (surf side)and on Bob Hall Pier...I usually just use 2 oz. silver spoons or 1/2 to 3/4 oz Silver-Blueback Rattle Traps...Should have plenty at Roys.
But live shrimp 4-6 feet under a cork will catch you just about anything...Just make sure and use a steel leader for the smacks, or you'll get bit of for sure if you don't...I just use the 12" or 18" (silver or black) steel leaders (pre-packed)30-45#or 60# prefered...
I'm headed to Packery Channel Jetties this morning,hope to be fishing around noon to catch the incoming and outgoing tides(High tide is around 2p.m, I beleive)...If no Smack action there, I'll go to Port A. jetties,,,,
Also heard of reports of a few slot Reds being caught South of Bob Hall on the shoreline, using cut whiting...
Good luck if you go...