TU for me in 2008 in OH.
EX for me in 2007 (when I got a denial) also in OH.
Wouldn't worry about missing out on the pre-approval if you wait 'til July. Where there's one Discover pre-app, others are sure to follow, I promise you! I took them up on the first offer that landed in my mailbox (as I was very excited to receive one, having been wanting the card enough to app and get declined a year previously!), and I received maybe 6 or 8 more within a few weeks, after I'd got my card.
If your original plan was to wait until July, I'd stick with it - the older your existing accounts, the fewer inqs you have on your reports, and the higher your scores, the better things are bound to go! If they want you as a customer now, they'll still want you in July... and maybe with a higher CL, etc etc.
i apped on 1st preapp i got too (12/08), also received several more preapps after approval. good that you're planning to app when you know you'll feel ready. i was denied on EX more than a year prior to my approval last december.
Just a heads up....I received a pre-approval from Discover in Dec. also. I put off apping until after it had expired. I did a cold app online instead. I was approved with a $5000 limit but did not receive the APR that I was offered in the pre-app. Several points higher...totally wishing I had waited to receive another pre-approval. I think you often get the best terms that way.
I'm in NV and they pulled EQ, my worst score, the only report still showing my 8 yr. old BK and the only report with my one baddie, a 6 yr old Dr. bill. They softed EX for the pre-approval.