True-ish. The only parts of LA you can hit in 30 minutes from Irvine are Compton, Carson and Torrence. Technically, LA, but if you're looking to go to Santa Monica, west hollywod, or whatnot, you should plan on on closer to an hour.
I used to do the reverse commute from OC to LA. Never again. The time above are assuming no traffic and what's maddening is that you find traffic in the oddest places at the oddest times.
Man, I want your car. Irvine to Ventura is 110 miles. You're averaging 88 mph. Even if you live on off-ramps in both towns, that's a pretty ambitious race speed.
You're right, San Diego in 1.5 hrs is no problem. Again, you have to worry about the 5 but it's definitely do-able.
I don't mean to quibble about drive times, but folks not from SoCal can get a distorted view about how close everything is in southern california because things seem closer than they are on a map.
Irvine to LA is 30 minutes if you're going to the southern reaches (think south central). If you're heading to Hollywood, Santa Monica, downtown, or most spots in LA, give yourself 45-60 minutes. Irvine to SD is about 1:15. Irvine to Big Bear (think skiing) is about 1:30 or so. All of this assumes best case scenario without a car on the road. If it's anywhere near rush hour, you just don't go. And you can easily add 20 minutes to any of these times for totally unknown reasons.