Yes, if you do a foundation in STPM / A Levels etc., it will be generally recognised by all private universities. But if you do a particular private college's foundation programme, it may not be recognised by others. I guess this is to prevent students from hopping between colleges.
You can check http://www.malaysia-education.com/pre-university.html for a list of the top pre-university programmes, and http://www.malaysia-education.com/diploma.html for diploma programmes.

You don't need super SPM results to get a place in many private colleges. Once you get a place, it's like a fresh start; a second chance - just work hard and smart!

Arts vs Science?
I think it's a real misconception to think that Arts courses would be a breeze. If you are in a good university, you'll soon discover that the volume and reading and the quality of writing expected of students in the Arts is very high. Then again, Science courses (as in Biology etc.) too require these. Engineering and IT, on the other hand, tend to be more numerical / technical and the linguistic skills are not always highly valued. The other factor is relates to thinking skills, as Arts tend to be more qualitative and Science more quantitative. Know your strengths and weaknesses.
Check http://www.malaysia-education.com and you can browse through universities and various courses.