BE90 pilot exceeds 1;500 FT prior to crossing WENTZ on the RUUDY 2 departure from TEB due to confusion.

Narrative

Incident took place on the RUUDY TWO RNAV departure from TEB. I was flying single pilot. Prior to doing the RUUDY TWO departure procedure; I reviewed it extensively; both prior to departure; and again in the run-up block just to have it extra fresh in my head. Although I have been into Teterboro extensively in the past; I had not been there recently. My ATC clearance was from TEB via the RUUDY TWO; climb and maintain 6;000; rest as filed. Mentally; I made the mistake that the 6;000 FT altitude that ATC cleared me to on departure from TEB overrode the 1;500 FT altitude to be maintained at WENTZ Intersection on the departure procedure. The climbout was in VMC. As I climbed through 1;700 FT (stopping at 1;800 FT; then descending slightly); ATC took note of this and said just to not do it again. At my end; when I was reading the departure procedure prior to the flight; I remember seeing WENTZ Intersection and being curious about whether the 1;500 FT overrode whatever ATC clears you to. TASCA Intersection (the next fix) has a clearly marked box that says '2;000 FT or as assigned by ATC' whereas WENTZ has a small box that denotes 1;500 FT. I wish I had queried ATC on that. Alternatively; I wish WENTZ was marked in stronger language on the chart (similar to TASCA); so that the ambiguity I operated in would not exist. I was fortunate that this incident happened in on a VFR day and there was no loss of traffic separation. However the potential clearly exists. I will be extra vigilant to question ATC on issues that I am not clear on during departure procedures.