"It's been a crazy couple of weeks," the four-star Costello said. "I've been very fortunate and blessed. I've been waiting around and hearing a lot of people tell me this and that about what I could be, but I really don't believe it until it happens. So it's been an exciting couple of weeks to see that schools are starting to jump on."
More schools could be joining the party sooner rather than later. Last week, Costello hosted a number of schools for a workout on campus, where he says he threw the ball very well.
"It was a pretty sweet workout," Costello said. "We had about six top schools there, in USC, Tennessee, Miami, Duke, Penn State, and Nebraska. It was on my spring break and they got ahold of my coach, and we had a nice big workout on Thursday. We had three or four of our receivers out there, so it was kind of a private workout deal rather than the whole team. So, it was nice, we got to do a lot of what they wanted to see. I feel like I performed well, so it was a good day."
UCLA hosted the 6-5, 205-pound Costello for a spring practice in April, and he said it was an opportunity to meet with the coaching staff in person and gauge their interest and style of play.
"Obviously, I've been talking with Coach (Taylor) Mazzone now for like two months," Costello said. "And then I got the chance to meet his dad, the offensive coordinator, at practice in April, so we're all building a really good relationship."
UCLA is recruiting fellow 2016 quarterback Malik Henry fairly heavily, but the Bruins may have a slightly different plan for Costello, should they choose to offer him.
"Coach Mazzone has compared me to Josh Rosen," Costello said. "They're just looking for a quarterback who's definitely a pass-first guy. They've got top receivers from all over the country coming in, and they want someone who can make their receivers look good. Also, Brett Hundley uses his feet and they want someone when the play breaks down who can pick up two or three first downs in a game. That's kind of what they're looking for now, and he says I absolutely fit their system. He said with Rosen committing, and things starting to settle down, they'll start to look at 2016 more. UCLA will actually be out to see me soon, along with Alabama."
As for his relationship with Henry, who joins him as one of the early top quarterbacks in the class of 2016 on the West Coast, Costello mostly laughs it off.
"Well, obviously (both of us) recognized that a couple of months ago when people started talking," Costello said. "It's a friendly rivalry. At the end of the day, we're each going to go to different schools. I have a lot of respect for him and I look forward to building a relationship with him down the road."
USC, the other local school, has started to pick up its recruitment of the young quarterback after the staff change through the initial communication into upheaval.
"USC, with the whole new staff, I was talking to Coach Kiffin and Coach Helton before the new staff came in, but then we lost contact a little bit," Costello said. "I think I've really started to connect with the new staff, especially over the last week, so that was nice."
Costello is still waiting on offers from both USC and UCLA, but he's hopeful that one could be coming from the Trojans fairly soon.
"With USC, Coach Helton said he would absolutely love to make a move on offering me," Costello said, "But he has to wait for Coach Sarkisian's approval. They got a lot of film on me from Thursday's workout, and Coach Helton is actually going around the country right now, but he'll bring the film back to Sarkisian sometime this week or the following week. I talked to (Helton) on the phone, we had a 30 or 40 minute conversation, and it was pretty nice. I'm optimistic. We'll see where it goes from there. I don't want to get ahead of myself."
In terms of a decision timeline, Costello said that he's still up in the air, but would like to have it finalized before he starts his senior year of high school. He cautions, however, that he could pull the trigger at any time.
"Along the road, if I really fall in love with a school, it could get done a lot earlier," Costello said. "I won't commit anywhere until I'm two or three hundred percent sure, but I'm going to take some unofficial visits this summer, and if something really catches my eye, I could be done this summer."