I am having mine outside in the courtyard at the Old Governor's Mansion. I know that you can do it outside at White Oak Plantation and there is also the 4th floor terrace at the Shaw Center. Hope this helps!
-magnolia mound plantation (owned by BREC on Nicholson)
-white oak plantation (owned by john folse)
-mt hope plantation (owned by lake house reception center, this is where I got married- LOVE it)
-lake house reception center (not sure the outdoor situation...)
-houmas house (20 minutes outside of baton rouge, but worth the drive- absolutely beautiful!!)
-the gatehouse (for smaller weddings)
-river terrace at the shaw center downtown BR
-old governor's mansion
---hope this helps!
fyi- a few of the best florists in BR:
-lance hayes (old hammond hwy)
-the cut flower (jefferson hwy)
Click on each tool to see a sample.