Honestly, I actually respect a ballsy woman. I've had one woman lasso me with an imaginary rope in the middle of the street. I couldn't help but laugh and smile at the situation. I was impressed... Then I realised she was from Oxfam.
As a guy it's a huge shock when a woman approaches us. I've had it happen a few times without me inviting them to open on me and i'm almost always caught off guard. It's not a pleasant feeling but you stay around. I would say however you approach someone on the street you've simply got to focus on making them as comfortable as possible after the approach. Don't give it much thought to be honest. If it's an opinion opener or observational opener(Much preferred) you can't go wrong with it in day game. I have approached a group of tourists looking at a map and asked where they wanted to go. They told me what they were looking for and I offered to take them there. While talking you just shoot the shit("Where are you from? Why are you here? What do you think? Do you like the people?" blah blah) then you can simply get their number by saying "You're pretty cool, give me your number and we'll meet up sometime." Then just leave and send them a text at around 9pm.