Unfortunately only one muster report of any of the companies of Pedro's regiment show up in the records. Nor have I been able to locate a regimental history.

You might try a Goggle search using any of the regimental IDs listed below, under "LA Cazadores Esp Infantry " there are a number of records in Spanish which may provide the information you desire.

George Martin

Pedro Barretos

Enlisted as a Private
"A" Co. LA Cazadores Esp Infantry

Company A of Lake Borgne, 5th Regiment, European Brigade, Louisiana Militia (Spanish Regiment), formerly Battalion Spanish Legion

Barretos, Pedro, Pvt. Co. A. 5th Regt. European Brig. (Spanish Regt.) La. Militia. On Roll dated New Orleans, La., April 2nd, 1862.

http://www.youngsanders.org/bnames.pdf