A few pieces of advice re Magic Mountain since I live about 1 hour from there.
If you're going in June expect it to be hot. I mean upper 90s type heat. You may luck out and have nice weather but be prepared for the heat.
Expect less than stellar customer service. The last few times we went to MM it seemed like everybody that worked there wanted to be somewhere else.
Obviously food and drinks inside the park are going to be expensive. It's not as bad as Disneyland but it's no joke. Of course if you're going without kids it won't be as big of a deal.
Whatever you do when you leave the park do NOT head north on I-5. You might end up in Bakersfield.
I'm going to disagree on the heat. It's typically only moderately warm in June, and often can be overcast, i.e. "June gloom", but we didn't get much of that last year. Usually July through mid-Sept is the hottest time. Still, summer dress is appropriate but bring extra layers, e.g. a sweater, light jacket, sweatshirt, etc. to throw on, especially if you're within 5-10 miles of the ocean. The fog can roll in and the temp can rapidly drop 10-20 degrees.