Head east out of San Antonio to Luling and hit City Market, then go north to Lockhart to hit Smitty's, Black's and Kreuz's on your way up to Austin.
Franklin's in Austin is a time commitment since you have to show up so early, but is well worth it. Salt Lick is pretty good BBQ and a great overall experience. County Line is not in the league of the other joints.
Mueller's in Taylor has always been excellent for me and worth the extra effort.
Remember to check out the hours these joints are open. Some of the best ones close early and are not open on Sunday.
Jim - Another transplanted Texan
Former KCBS CBJ
Large and Medium Big Green Eggs , Black 18.5" WSM, Blue Weber Performer - Stainless, Green Weber OTG Kettle , Brinkmann SnP Pro, and a Stainless UDS. One retired Portable Kitchen grill.
Red Thermapen, Maverick ET-732, EdgePro Apex Sharpener.
Avatar is the original 1951 Weber Kettle