Several years back, I came to realize the painful truth that a degree or certification doesn't necessarily mean much -- if anything -- in terms of teaching ability. One of the best teachers I ever hired had very little previous experience (just a gifted teacher, born to do it) and one of the worst had her MA in TESOL *and* was certified by a large local public-school system. She couldn't teach her way out of a paper bag, and in fact got frustrated and quit in the middle of a term by leaving a resignation note for me written in pencil on the back of a handout -- in her classroom, for the students to find and bring to me. It was definitely a lesson for me. (And to cap that experience, she later used my name as a reference!)
There is a great deal of difference between knowledge of a subject and ability to impart that knowledge to others.
What certificate or degree programs in TESOL can give you is the knowledge of best practices in the field. Only you can know if you have the passion and the drive to work with Basic ESL students -- and that can be the most rewarding, frustrating, energizing, exhausting, wonderful experience in the world for those who do have that drive.