Just the two of you on New Year's Day... hmmm...
Well the Valle de Guadalupe wine tours are nice. You get to taste some surprisingly good wines and have access to regional goodies like olives and olive oils.
New Year's Day may be in interesting day... quiet.
The weather in Valle de Guadalupe will be nicer... probably. It is not that far away, but over in a valley not on the coast... so you generally get more sun and warmer weather.
There are some sports bars downtown where you could sit and watch the football games, drink Mexican beer, and eat casually. If you are a football fan, that could be fun.
Hope this helps give you some clues... and that you have a good day!