chances of getting a bid as a freshman at blinn

Depends on if you know anyone in those fraternities already. Sig Ep might be difficult if you're not already close with the guys based on your high school/hometown connections. I don't even think that they have a lot of Blinn Team. It's worth a shot though. You should be fine at the other houses you mentioned. You could also wait until you're full time A&M in the Fall and spend the Spring semester making connections. Lots of guys here join in their Sophmore year anyways.

Nah man rush anyways they 'may not take blinn kids' but they may actually

Every house will take a blinn kid. But what the others said is also important. Getting to know the people in the chapter is incredibly important because being straight Blinn is a hard ding to overcome. You're gonna need a lot of people in the room pulling for you, and if you're just 'eh' then you probably won't get a bid, at least until you're full A&M. If you're positive you're gonna be in next year, I would take the spring and get to know the guys at your top choice rather than take a spring bid from a lower house like sigma chi or kappa Sig. That's because being a pledge while you're full A&M offers you more opportunities like being able to be on EC, IFC, etc. that blinn (the university doesn't know they exist) aren't afforded. Also, being a fall pledge is way better than being a spring pledge across the board.

Delt doesn't take blinn kids.
I'd say wait. Fall pcs are always better.