"Expensive" is "drága", but we can't add a negating suffix to it like English adds "in-", so yes.
"Olcsó" is similar to "cheap" in that it can have different connotations in different contexts. It can simply mean "inexpensive" or "nem drága", but it can also mean poor quality.
In standard Hungarian, it's a "light l" which means your tongue is in front, "alvio-dental" as the jargon goes. A more rural version is with a diphthong or even a straight long vowel, something like oucsó or ócsó. The so-called "dark l" or "velarized l" is basically nonexistent in Hungarian - it's either the "light l" or no l at all.