I would say the best thing you can do is go to tempe town lake at night.
It is the best well lit, but still romantic at night place you can go to. Many places to eat and drink right there a block away at mill and the new light rail is near by too if it fits your driving schedule. Awesome little boats they rent that you peddle on the lake in and legendary AZ sunsets = you know what. lol jk.

Very close to mesa like 12 min away that is the place you need to be for sure. Get some dessert on mill ave after and walk your way north past the shops and to the park area. VERY SAFE they got police mounted and on bikes near by as well as other couples walking around. I was never really crowded there though plenty of privacy and just gorgeous.

Hope i helped, enjoy!

check the site out!