If you look at Hardee's and Casey's Tactics (not tactical manuals at all but, rather, drill books) both mention left and right guides for each regiment along with the unit colors as ways of posting and guiding the regiment in battle or in line.

So in answer to your question, yes the LA units would have had guides on the flanks.

The US made so many swallow tail cavalry guidons that these were often used as guide flags for Union infantry regiments.

Greg Biggs