I'm looking for a cruiser style bike, with the sweeping handles bars. I'm looking for something that I can use to just ride around the neighbourhood, it won't be for commuting for anything. I want something that can optimize the amount of speed I get for minimal effort, which I know has to do with the gear ratio. Would a single speed, 3-speed, or 7-speed cruiser be best?

I'm a 5'11" female, I don't really care about the cosmetic differences between men's and women's bikes. I just want something functional and long-lasting. So based on my height, what size frame do I need? And can anyone recommend a good brand that has what I'm looking for for under $200 or so? Like I said, I'm only looking to use this bike casually, so I'm not willing to spend more than that.

I'm not interested in looking in local bike shops, as all the ones in my area sell only the newest, expensive, high-end bikes (no used bike stores), and all the big box stores pretty much sell mountain bikes. I'm looking for a deal online.

So, any suggestions/tips/advice?
I'm also looking for an affordable bike trailer that I can use to haul small garden tools and my 2 kitties to my rented garden in the summer.