In answer to your questions...
Must feel like South Africa - sailing the 'wrong way' (port wave riding)?
Do you notice much of difference (port vs starboard)?It feels a big strange at first but after a couple waves I adjust. Helps that I've done pretty even amount of sessions on port and starboard.
Looks like Topocalma is about an hour and a half away south of Matanzas, correct?
Actually it's only 45 min on gravel roads, plus the 3km on the sand. It's about 10 minutes away from Puertocillo a surfing beach which currently has a few places to stay but is about to be massively developed with vacation homes.
Looks like Roca Cuadrada is also in Matanzas, is it along the same beach or is La Roca Quadrada a different location?
It's at the southern tip of the bay next to matanzas city. You can walk from either Matanzas or Las Brias (25 minutes either way. For sailing you can drive there, technically not aloud. Or sail upwind from Las Brias in a couple tacks.
Can't seem to find Papuya? South of Matanazs about 10 mins by driving or an hour walk.
Details
It looks like you took your gear with you. What airline did you use? American Airlines $150 per kit.
Where are you staying? Are you able to sail from the Cabana's where you are staying? Hotel Alba right on the beach, you can sail out the back door to the point at Matanzas.
If not, are there places where you can stay that are walking distance to the launch?
Hotel Surazo - much more expensive for hotel but has camping spots right on the beach, closest to the launch. Was one of the original places so lots of windsurfers congregate there. They have a limited supply of boards to rent but all nice goya quads. You'd have to contact them first in high season because I suspect availability is limited.
A hotel called Roca Cuadrada - also on the beach.
Olas de Matanzas on the hill over looking the windsurfing spot - expensive but offers both cabins and camping.
5 mins walking is a large campsite with nice sites which would be a good budget option if you want to bring camping and windsurfing gear.
Lots of cabanas on the surrounding hills - some on air bnb and vrbo. But you'd probably get the best deal if you showed up and spoke Spanish
If you were to go again, where would you stay?
Depends on duration. Lots of nice houses in Matanzas for longer term. Possibly Puertocillo to be close to Topocalma. Less amenities here though. But apparently in the middle of summer Matanzas can get busy on a point break. Windy season starts in October but things are still quiet now. They apparently get busier in Dec/Jan
Did you have/need a rental car the whole time and upgraded to 4X4 for Topocalma?
We had one the whole times since a few articles we read all highly recommended it and regretted it when they hadn't spent the extra money on it as it can extend your options for sailing (Topocalma, roca quadrada)
Approximate total cost?
Can be done on a super budget if you camp and just sail Matanzas (no 4X4). You can spend as much or as little as your budget allows on food and accommodation.
Airfare - depends how far in advance you book but around 1100 plus gear each way $150
Car - 4X4 is the big cost $1300/2 weeks
I burst out laughing when I read this as I immediately throught of the Oregon Coast. I have very strong memories of sessions where it felt like I spent every moment on the water looking for a safe place to hide. 
That looks soooooo sweet! 
So jealous it hurts. Thanks again for the pictures and info Ryan and Jen!