There is only one place on the strip that has 100nl, and that's at Bill's Gambling hall. It plays like 0.05/0.10 online for the most part. Last time I played there, there were 3 regs at the table, only one of which was even remotely average. One was weak tight and the other one was a huge fish that would shove with top pair no matter what. The rest of the people were all tourists that barely knew the rules of poker.
Everywhere else, the lowest limit is 200nl. I've played 200nl at MGM, Flamingo, Harrahs and Mandalay bay. Of those, it just depends on the table from my experience. I had a brutally tough cash game table at Harrahs on a Tuesday afternoon once, but of the 2 MTT's I've played there, I bubbled one and I won the other and the play was terrible both times. The softest table I ever had was at MGM. I actually started feeling guilty after about an hour and a half because I just ran everyone over, but like I said, there is no golden spot of softness, it's table dependant.
As a general rule, what you will end up seeing everywhere is a lot of limping by lots of people. People don't get on a plane and fly to Vegas to fold.
If I had one suggestion, play at a poker room that is easy to see and convienent to get to. This allows for a higher percentage of casual players to walk past and just sit down to play. The rooms that are hidden off in a corner somewhere tend to get people that are actively looking to play poker. I think thats why MGM was soft, it is out in the middle and easy to see.
Also, pay attention !!!! You will be able to pick out the fish quickly if you pay attention to the hands you aren't involved in instead of oogling the ****tail waitresses.