Biosphere Reserve

It's a very beautiful place to come and visit, and see a lush mangrove forest. The area is also occupied by several groups of monkies, who will openly approach tourists (watchout for the grey ones near the entrance they can be aggressive and steal things).
It can be a little overcrowded on public holidays and weekends, and make sure you bring an umbrella/raincoat, there is only one place to buy a poncho in the area, and it's not always open.

If you are interested in traveling to Can Gio, I would recommend doing it as an small, organized day trip from Ho Chi Minh. I did not and did it solo as a two day, one night at Can Gio Resort. The people there were lovely, but as a tourist the part of the reserve to explore is limited and can be done in one day. Most people I encountered speak limited English.

To get to Can Gio you can take a Vinasun Taxi or Grab, but here are other options. Bus 75 leaves from Ho Chi Minh and travels to Can Gio three times a day. It currently includes the cost of the ferry ticket and they load the bus on the ferry. You can also take Bus 20 to end of line and walk to the ferry. This bus runs very frequently from Ho Chi Minh. Once you get to the ferry, ride the ferry across the river and then get on Bus 90 (every 30 minutes) from Binh Khanh bus stop just beyond the ferry exit.
Bus 75 is 30,000 VND, Bus 20 is 6,000 VND, the Ferry 1,000 VND, and Bus 90 is 6,000 VND at time of writing. Costs are posted and on the ticket. I ended up taking a Grab to the ferry, riding the ferry, and then catching Bus 90. A couple tips for catching the Bus. You must flag it down. They keep the buses moving and they don’t stop unless someone requests. If you are traveling with a large bag be prepared to buy two tickets. Day bag is ok.

I found the Moovit app very useful for this route.

To get to Dan Xay, the app says the stop is Tram Tang Ap So 3, but I found there is a stop right before the bridge. Let the driver know that is where you want to go and they will probably rolling stop right out front. I stopped here and walked along the bridge, but did not do any of the activities. Prices are posted.

To get to Monkey Island, the stop is Nga Ba Dao Khi and the stop is right next to the entrance. Again, let the driver know or flag the bell when you see the stop. About 800 m down the road is the ticket office. Tickets are 70,000 VND for foreigners and another 10,000 VND. You can walk to the Rung Sac base or pay another 600,000 VND to get there on a boat (per boat/not person). The boat ride takes about 7 minutes to get to the base through the forest and same to return. If you are dead set on taking the boat, pay attention to the tide schedule. The boat does not run during low tide.

The bus stop to Can Gio Resort is 30/4. This is not near Can Gio town which is further along the route.

There are bus stops on both sides of the road in Can Gio, just go to the side in the direction you want to travel. Bus fare was good for one ride, so you pay 6,000 VND each time you get on. Cash only.

Good luck!