That Nashbar Flat-Bar Road Bike that was linked doesn't look too bad. It's got components that are consistently a grade above the more expensive Diamondback, all across the board. Quick release front and back, 8-speed cassette, Acera and Altus instead of Tourney or worse...
I can't recommend enough to take a trip to a local bike shop and listen to what they say. You will learn about proper fitting that can prevent injury (won't happen on a *one size fits all* cheap bike) Test ride different bikes. You might think you know what you will want/like .. but that may be blown away once you test ride. I would NEVER buy a bike where I am not given the opportunity to test ride. Had I done that back in '01 .. I would have laid my cash down somewhere else.
I have spent times over what I did back in '01 this past year and I have NO regrets.
Personally, I would never ride the darned thing, and most around here would never want to ride the darned thing. It is absurdly heavy (I have a "heavy" touring style bike, but he enjoys doing one armed curls with it since he can't do them with his own). It isn't comfortable enough for me. But he has a great time, it is no coat hanger in the garage, he's staying in good shape on it. He stays in better shape on it riding 20-25 miles than I would on my bike riding 20-25 miles. He has no complaints.
If your goal is to ride on pretty flat terrain and get up to 10-15 miles, and nothing more, you'll probably be fine on one of the bikes you suggest, or a cheap beach cruiser. If I were in your shoes, however, I'd try to follow the suggestion of others and look at used options. Garage sales, craigslist, bike shops with used, other sources for used. If you don't want to buy too cheap in case you enjoy it, then spend a little time to find something used that you can test out first to see if you like it. You'll get more bang for the buck and you'll get to test ride. How can you go wrong? The biggest danger is that it makes you more likely to enjoy it, and then you'll start riding more, and then you'll decide you want a better more expensive bike. Get a cheaper bike that is less comfortable and harder to ride, it is more likely that you won't enjoy it and won't have any desire to spend more money down the road.
As a 58 year old geezer with a bad knee.. I went with the Electra Townie 21.. and we LOVE IT... to the point my wife got off her Trek and we found the ladies Townie to match this year..
they are easy to ride.. very stable... I'm riding it 25-35 miles with out any issues..... NOT a mountain bike.. great bike path, road, park bike... has front suspension so the ride is good, but it's the feet forward design that got me back on a bike again... my very high end road bike has been sitting for 15 years, as my knees just don't like that frame style any longer.... they are pricier.... I picked mine new at REI for $525, but found wife's on craigslist after a few weeks of watching the posts for $225...
Love the Townies.....
Lots of great answers. I began riding last July and after searching around on the internet I found this terrific site and it's over 50 forum. Couldn't ask for more. I'm almost 72 and began last summer after not riding a bike for 43 years. Sad to say you get what you pay for. Good quality new bikes simply cost many hundreds of dollars now a days. I did a moderate amount of research and settled on a Trek FX 7.6, yes, around $1200 at a LBS. I don't regret my decision one bit..and truth be told I could have been as happy with two models below in price. I've got 2930 miles on it through a few minutes ago; 1700 miles on my indoor trainer and the balance on the road. I ride on trails here in northern Virginia weather permitting.
I was originally 222# two years ago and have dropped to 180# and stayed there since buying my bike; my resting heart rate is now 52 and my doctor stopped my blood pressure medicine. I realize that that may not happen for everyone who takes up cycling but after reaching retirement bicycling is an ideal way to make sure you can enjoy retirement and not simply watch yourself wind down till it's over. Perhaps a used hybrid model is in order. Fortunately athletic equipment has a low usage rate, most people having more enthusiasm than follow through. I'll bet you can get a nice one on Craig's List, through the paper, or at a shop. Buying a department store new bike is asking for trouble if you plan on settling on 10-15 mile daily rides. By getting a sound, better quality used bike you can see if it's for you and then save up for a similar (or better) quality one if you like riding. Good luck!