How easy is it to learn the cello?

Now, I know that learning any instrument isn't easy, but I just want to know how much time it would take to be able to play the cello fairly well. I already have a musical background (clarinet and oboe for five years, piano for six) and know how to read both treble and b clef. During the summer last year, I decided to take cello lessons for fun with my high school, and I thought I got off to a pretty good start for never playing a stringed instrument before. uming that I took 30 minute lessons every week until September, and practiced every night, would I be ready to join my high school orchestra? Of course, I've talked to the orchestra teacher, and she says that I can join no matter what. I just don't want to be embarred... And, if cello really is such a difficult instrument to learn, what stringed instrument is easier (violin, viola, b, etc.)? Thanks!