My son is almost 2 and only speaks 20 words, also doesn't say two word sentences yet. Will his doc test for autism or speech delay at his 2 yr appt?

Screening is key. There are screens and questionnaires utilized by doctors during health checks, which help to detect delays in development, including speech. If there is concern, further evaluation will likely be recommended in those cases.
See pediatrician. If your child's developmental landmarks are normal except for the delay in speech, a hearing test may be ordered. You do not indicate how many children you have. Birth order can relate to delay in speech production as second or later children may exhibit speech delay but communicate in non verbal manner. does Screening for autism is recommended at this age for delayed speech.