When I first moved to India at the age of 16, I landed in Mumbai and stayed there for several months. I landed in April and it took some getting used to. It was so hot and humid!
I think because I'm not such a "big city girl," I preferred my time in Lonavala and Pune, neither of which are far from Mumbai. Lonavala is so green and peaceful out in the hills, and I lived in Pune for nearly a year and a half, so got to know the place very well.
There are some lovely spots in Mumbai. I remember one restaurant I went to, during monsoon, and I watched the rain falling outside while I sat inside and drank chai and tried something new on the menu: chana bhatura. It became one of my favorite dishes. ;)