Welcome to 'the club'.
This will probably turn into one of those 'what's your Lactate Threshold and unless you know what it is we'd all be guessing' threads.
A link - take it for what it's worth
http://www.bicycling.com/training-nu...-threshold-101
So unless you know what your LT is... we'd be guessing.
As for HR zones - don't go with the 220-age deal. I can ride at my 220-age = MaxHR for 30 min+
One calculator I looked at told me my 'target for vigorous exercise (70-85% MaxHR) ' is what Mr. Friel is calling my Zone1 and 4 bpm into Zone2. That's a 'dude, wait, what?'
Advice I could give would be to keep ridding and get as many miles in as you can. Your fitness will improve, probably by leaps and bounds at first, as you put miles on and the weight comes off.
Ride hard when you want and then ride casually when you need to recover.