I don't hang out at the races (at least not since 1986), but I'm aware of them through what others have said, and reading about them in the papers. Among the places that I'm aware of are Kearny Villa Rd near 163 and I-15, and also places in Sorrento Valley. My understanding is that most of it occurs Saturday nights, but I'm not really sure about the times and locations, since the police has been cracking down as of late. Also, I see loads of cars cruising up and down Mira Mesa Blvd around those times, and also hanging out at various eating establishments along that street.
As for legal racing, I believe they do 1/8 mile drag racing down at Qualcomm Stadium.
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1995 NSX-T
1999 3.2TL
2001 Odyssey
1992 SC400