Miljam,
The 50 miler has one hill .9 miles long that is a pump and only 1 or 2 other short hills that can be called hills. The rest is failry flat or down hill. What is your longest distance to date? This one should be a good one for you.
Since you are in San Marcos, not a long drive, maybe you can join me Saturday morning? I'll be leaving the South Shore parking lot at Mission Bay (just off Sea World Dr) at about 7:30 AM.
CycleFrog