Is there access to Texas Cruise boat at this park?

No black Rock is west side the cruise boats are on the Northside. You can get a map of Lake Buchanan at most gas stations and you can see both places and how to get there.

Does it have boat ramp to go boating

In the four years we've stayed 5 nights per year, I've not seen that to be the case. But I'd just call & ask them directly to be sure. ..