"My chief concern are groups transporting drugs as in most cases the illegal aliens do not pose a significant threat."
Gotta disagree. People being smuggled are a commodity, just like drugs, guns, $, ect. Always assume the Coyote is motivated and mission oriented.
Put yourself in his boots...He has walked into a kill zone. At least one concealed shotgun/operator is covering him...maybe at spitting distance..his menu of choices severely minimized. The obvious; stay alive, keep the inventory/product safe, get to the destination.
Everyone was lucky on this one.
Use the buddy system hunting down south ( yeah I know..."Yes Miss Landers") and take ericb's advice..have a high capacity sumthin.
In this case..maybe a discussion of the Dos and Don't s of revealing a concealed position of advantage.
Know your AO: the border has been dangerously porous for a long time now so encountering illegals shouldn't be a shock
Always carry anti-personnel ammunition when hunting: a pouch full of 00 wouldn't be that much of a nuisance to carry on your belt
Always carry commo: there's cellular coverage along most of the Texas/Mexico border outside the Big Bend area
Have the local Sheriff and the Border Patrol programmed in your phone and call them at the first sign of border-crossers
Retain tactical awareness even if you're there for recreational reasons: have an escape route planned and avoid locations that are neither defensible nor allow a speedy covered/concealed exit
It's not a bad idea to have armed friends within earshot, nor to have let people know where you're going and when you plan to be back
Quickest way to tell if you're looking at drug smugglers rather than "ordinary" illegals wil be what they're carrying. Mules will be loaded like, well, mules. A big packload of product on their back versus a water jug and a plastic grocery bag with some personal effects. Mules aren't likely to be armed, but there's a fairly good chance there will be armed escorts not too far away.
As for announcing your location? Sounds like at least the guide already knew there was someone in the area. Announcing your presence isn't going to hurt much at that point. If you can remain unseen it can give you a tactical and pyschological advantage. Bluffing that there is more than one hunter present would not be a bad idea either.
Watch for anyone using a radio or cellphone, or trying to maneuver around your location. That should be a red flag that these are more than potential landscapers on their way to the promised land, and it's probably a good time to start your E&E.
If you see weapons? Flee if you can. They're not a raiding party looking for scalps or prisoners. Unless they think they can prevent you from raising the alarm, they're going to clear out, dumping their loads most likely.
But if they can get close enough, they might well kill you, figuring they can deliver their loads and be back over the border before anyone finds your body.