I also think aiming for 80-100 RPM makes perfect sense. On solo rides, that's where I feel most comfortable. When I ride solo or participate in time trials, I usually push harder rather than spin faster if I want to go fast. I try to never drop my cadence below 80 RPM though, because I feel I tire myself much faster under that limit.
But when I ride in fast paced group rides or road races, without any conscious effort on my part to do so, I end up spinning much faster. I'm usually around 95-115 RPM in these circumstances. I don't know, for me, it just feels natural that way.
Getting a cadence meter is a good idea. Go out, ride and take a look at the cadence when you feel comfortable in a given situation, i.e. on the flats, while climbing, descending, etc. Also, try to change pace once in a while, to see how different cadences feel in these situations - sometimes, the cadence that feels instinctively most natural isn't the one you'll be able to sustain for the longest period. Always note mentally what feels best. At some point, you'll find your sweet spot. And when you've found it, you probably won't need the cadence meter anymore : spinning at the pace that seems right will be enough!