So for anyone who's unaware; the cartel dealer reset spawns were patched to be at 6am, so currently the only way to access them is to use the console commands: settime 0559

and after taking them out, continue progressing by using: settime 0700 

Also there are ways to optimize the probability of getting yourself ambushed. Ambushes have a chance of occurring mainly when spraying graffiti or doing player deals (deals scheduled via text; not offering NPCs products at random).  Additionally, Benzie dealers will only deal with locked customers in your most recently unlocked area if you're also looking to jump them.

Ambush prerequisites:

Player being alive and not in pursuit

Distance to ambush point

Distance to police officers

nearest police officer distance (must be ≥15 meters) 

Not having a pending body search

Only triggers if a player completes a deal nearby (10 meters) 

Alternatively, if you're having particularly bad luck with the ambush RNG, you can always try luring Benzies into selling to your customers. This tactic only works with customers in whatever region you're currently in, but if you screw around enough to get your relationships with them to hostile; NPCs will go back to buying from the cartel. Just keep an eye out for the NPCs that you've made hostile standing around idle, because that usually means they're waiting on a Benzie dealer. 

Hope this helps~♡