To get to the official start of La Milagrosa, you need to first begin with a miserable hike-a-bike up about 500 vertical feet over a little less than a mile to the top of the ridge on the Bellota AZT. Then continue down on the Bellota AZT until roughly the 2.5 mile mark where you'll come to a junction. La Milagrosa official begins to the right heading south. Or you can continue to the east on Bellota AZT all the way to Reddington Road.
That said, La Milagrosa is a fun, fast, technical, gnarly, rocky downhill that can easily throw you over the bars if you're not prepared. If you're wondering if you should suffer through the initial hike, the answer is yes. It's a great ride definitely worth doing at least once a season.