I hiked this yesterday for the first time from the Tenaja Trailhead parking lot and it took about 1hr 30 mins to the fisherman camp sign. Does this trail lead to the waterfall or is that to the left when you reach the fisherman camp sign?

Sounds like you started from Tenaja Trailhead (with bathrooms). If you drive a few more miles down the road, you reach the Tenaja Falls Trailhead and the falls are less than a mile from there. To answer your question, once you reach Fisherman's Camp, you continue right and start uphill, then a sign points to a branch left along the slope to the falls. I think it is 7 miles one way from Tenaja Trailhead to Tenaja Falls.

I drove about 3miles on that narrow road that leads to the Tenaja falls but I turned around back to to the parking lot instead. I didn't wanna risk the chance into bumping into someone on those curvy turns.

The trail to the falls from the tenaja parking lot only takes about an hour if not less to get to the falls. There's signs that point the way. Once you hit the fisherman's trail deviation you go right

Generally if you go on a weekday like today you shouldn't see many if anyone on those curvy turns. If you go on the weekend you'll have a much harder time. Even if you happen to bump into someone there are quite a few areas you can pull off to the side of the road. Many drivers are cautious through there and many times I've noticed people will pull over for you until you pass by them.