**No—you cannot use your C-1 visa for a separate trip from Jamaica to Miami to visit friends**, even for just a couple of days.

A C-1 visa permits **immediate and continuous transit through the United States on your way to another country**. The State Department explicitly says that a stopover to visit friends or sightsee requires a visitor visa. Multiple entry allows repeated qualifying transit trips; it does not expand the permitted purpose of your travel. [U.S. transit visa guidance](https://travel.state.gov/content/travel/en/us-visas/other-visa-categories/transit.html)

For your planned Miami visit, you would generally need a **B-2 visitor visa or a combined B-1/B-2 visa** before travelling. Visiting friends is expressly permitted under B-2. [U.S. visitor visa guidance](https://travel.state.gov/content/travel/en/us-visas/tourism-visit/visitor.html)