I have seen "i hope so" as "mam taką nadzieję". How is this different, if at all?
Adding "taką" points out more clearly to what was said previously. But it is not needed, the context makes it clear anyway what you hope for.
How does one say "I hope" in Polish? For example: "I hope I get accepted into this college?" or something like that.
Also "Mam nadzieję". There is no equivalent to "so" from "I hope so" because what is "so" should be known from the context.
"Mam nadzieję, że przyjmą mnie na ten uniwersytet/do tego koledżu/do tego college'u." (that they will accept me)
"Mam nadzieję, że zostanę przyjęty/przyjęta [...]" (that I will get accepted)