Conditionally Hide Rows Based on cell

Can you use macro or would you rather use formulas if possible?

To use a macro the sheet has to be macro enabled and you'll have to add code and so forth.
To use formulas, you may have to put a formula in every cell that you want hidden or not using an IF() function. You will link your dropdown to a cell, this cell will then show a 1, 2, or 3 depending on the selection. Then in the data cells you'd have like a 'IF(A1 = 1, "text for first selection", "")'. That's off the top of my head, but if the linked cell A1 has a "1" in it because they selected the first item in the drop down, the cell would show "text for first selection" but if they chose item 2 or 3, the cell would be blank.

Hope that helps.