Speed Uno is a great option. Another option if you want to play it safe and get a bike with gears is the Dahon Eco 6. Also at thorusa in your price range. http://www.thorusa.com/dahon/current/ecoc6.htm

I got a Boardwalk with no gears and couldn't even go up a speed bump so had to upgrade! Of course, I'm not as physically fit as I used to be but if you want to a bike with gears, I would also look at the Eco 6 or Speed D7 (higher price but a REALLY good bike)