In the LA area, both Regal and AMC have a number of IMAX 70mm theaters. Universal City AMC and Irvine Spectrum Regal both have the biggest IMAX screens. TCL in Hollywood has the next biggest. The downtown Regal and Burbank AMC are in the third tier (bit still very large).
All of these theaters have IMAX 70mm film projectors.
Huh, I'd only seen IMAX at the California Science Center and it blew my mind at the time. But according to this article and site below, apparently haven't really seen IMAX:
All of these theaters have IMAX 70mm film projectors.