Yep, I would join the PSA Collectors Club with the 15 free grades, and send in your higher values cards on that one that apply. Then use one of the monthly bulk submission deals (this month is $6 per card Pre-1956 with a minimum of 25 for a 50 business day turnaround).
http://www.psacard.com/Specials/
Some people who send all of one year in at a time get faster grades and turnaround since there is little research to do and they all probably get processed at the same time.
Here's my other suggestion: if these are your second best cards, don't send these yet. Send your best cards. If you are happy with your second set being raw, you'll make more money on your best cards getting graded. Why send the PSA 7.5s when you might have PSA 8s and 9s you're not getting graded? That's how I would see it.