Unlock conditions
Most markers appear after The Leonida Job once you have free roam in the Keys and Vice Beach corridor.
Suggested order
Hit the Keys bait-shop chain first for a permanent discount, then double back to Vice Beach for the street-racer intro — it unlocks street racing pins on your map.
Missable flags
Declining the first phone offer from the bail-bonds contact locks out a unique muscle-car spawn until NG+.