It is helpful to have some experience programming before taking 120. It is not expected that one have electronics experience before taking 121. Astro 120 can be taken as a sophomore but is usually taken by juniors. It involves a lot of coding, probably in an analysis package called IDL, and leads up to some pretty serious stuff, like precisely measuring the period of the Crab Pulsar. You don't really need previous programming experience, although it definitely helps.
Past students say that they enjoyed the course immensely.
I loved it because it is so different from all the lecture courses. By the way, IDL stands for Interactive Data Language and it is used to analyze data by writing programs. Almost all of the labs will revolve around building and using microwave receiving systems, with the coding coming in later in the semester as the coursework moves into interferometry. See the class web page for more info. Two physics courses can be counted toward both the physics and astrophysics major.