I may curse myself later but I will share my hints for getting to and fishing the end of las Conchas.
Step 1 - If you act like you belong there, the guards let you through. Even if you look like a hoodlum, they will probably let you through. Life has taught me that low level security guards are just in it to draw a check. Those guys probably get paid in animal crackers so they pretty much let anyone in ....
Step 2 - Do not attempt unless you have a sand worthy 4x4 or not afraid to walk great distances or spending half your day shoveling out your truck. Plenty of beer should be packed for the occasion in cases of emergency (You need someone to dig/pull you out).
Step 3 - Go to very end of las Conchas. Right before the entrance to Tessoro you can take a left.
Step 4 - Ignore the "Do not Enter" signs. Ehh, everyone else seems to. Go down and take a right at the road. It will take you down a steep sand bank into the estuary area. If you have doubts on the sand capability of your 4X4, proceed to back out before heading down the sand bank and fish elsewhere or pack plenty of beer for a good walk.
Step 5 - Once in the area take a right and head to the open water (Southwest). Park in a safe area based on the tide coming or going.
Step 6 - The tidal range can be significant. Keep a sharp eye out for stingrays in whatever direction looks promising to you (I will leave this up to you to figue out) Stingrays can be plentiful wading in and out of the area.
Good luck and have fun. Tides are an important key in timing in which I have yet to master completely in this area particularly if you want to fish the reef. This is one gnarly rock that will tear you up unless you have some good footwear.
If you see a Dark Red F-150 down there, feel free to share that extra beer you brought down in case of emergency.