Most large casinos have doormen and taxis at the entrance, especially those with hotels. You can always have the casino call you a cab where they don't have a stand out front.
I used to walk around with 5K or 10K in my pocket. In Vegas you're pretty safe in the daytime, but if you get into a session until 2 or 3 or 4 in the morning, the streets and self parking facilities take on an all together different character. I leave my money in the bank or hotel safe now. Just carry enough for a session. Also, its worth it to leave your car with the valet service; then you don't have to sweat the deserted shadowy streets and long hallways and empty parking lots. Know your casino. I wouldn't be caught dead walking back alone to my car from Circus Circus with a sizable bankroll. On the other hand, a valet service or cab at Mandalay Bay is fine with me.
If you make a really big score, the casino may have safety deposit boxes. You can leave your chips or money and come back in the daytime to get it. Archie Karas had millions in chips at Binion's for a couple of years (until he lost it all). He would only take out ten thousand dollars at a time to gamble. The chips are not taxable until you take them out and cash them in. At ten thousand they become reportable to the IRS when cashed, so always cash out less than $10K.