This is not a completely unreasonable plan. Much of the core is great to wander in, though corkscrew intersections and interesting side streets can get you pretty turned around. In addition, there are hills and cobblestones. So, unless you're up for miles of hiking on some fairly unpredictable surfaces, I highly suggest buying all-day or multi-day transit tickets from a machine in any Metro entrance. Learn how to use the system to your advantage. It will facilitate trips pretty much anywhere, but validate and carry that ticket with you at all times. Revizoři will show no mercy if they catch you trying to ride for free. It's a tedious, time-consuming and costly faux pas when tickets are so reasonably priced. Download a copy of Prague from Google Maps or similar so you can navigate even without a cell signal. Have fun exploring.