I am a 25B, information technology specialist. How likely am I to get my Army reserve unit to send me to a Sec+ class on orders??

Short answer is: You can very likely get the certification paid for, but it's unlikely you'll be paid to attend a bootcamp unless there is an immediate operational need (needs of the Army, that is) for you to have one.

Longer answer:
You may be able to get your unit to justify sending you to this course as part of an AT plan so you can at least get paid while you're attending. You can also just use you GI bill for these courses. Overall, it depends on how much you can sweet talk your chain of command and unit admin. Are they invested in you or can you demonstrate why you having this certificate will help the unit more than you attending battle assemblies? This website may have some useful informations, forms and regulations which you can use to help build your case:

https://atc.us.army.mil/iastar/regulations.php

https://www.cool.osd.mil/army/index.htm

Lastly, you really don't need a Sec+ bootcamp. Just spend 2 months reading the book and taking the test preps online and from the book. Then test. Bootcamps are a scam.

Some installations are offering them, check your nearest Ed Center. ASG Kuwait has an enduring Sec+ program for example.

That is a specialty course that isn't in the CA unit training tree for your MOS.
The shortest answer I can give you and the one with the best chance of success is for your commander to determine that he/she has an operational need for this capability and write up a ONS (Operational Needs Statement) next time the annual planning cycle gets briefed.
There are missions out there where this would be useful (Atlantic Resolve comes to mind), but whether your unit is one of them I can't say.