To me it seems they really didn't like him. I mean Willie was always so angry and yelling at him. Kate constantly complained about him. Lynn was just so mean to him in the final season. The only one who seemed to like him was Brian. Just watching reruns on HULU it seems they didn't really care for him so why hide and house him?

I think ALF took awhile to endear himself to Willie and Kate. If they really didn't like him, I'm sure they would have turned him in to the Alien Task Force pretty quickly.

Willie, Kate, Lynn and Brian (and certainly Lucky- lol) all had issues with ALF at some point or another- they all got into arguments and got angry with him at some point- just like any family. (The same interactions happened between the humans in the family too.) Numerous times on the show it was shown quite clearly that they all really love ALF- especially Willie.
See episodes "A.L.F." (pilot), "On the Road Again", "Help Me, Rhonda", "Going Out of My Head Over You", "Try to Remember" (Parts 1 and 2), "ALF's Special Christmas" (Parts 1 and 2), "Oh Tannerbaum", "Jump", "Working My Way Back to You", "Somewhere Over the Rerun (AKA The Ballad of Gilligan's Island)", "Some Enchanted Evening", "Someone to Watch Over Me" (Parts 1 and 2), "You Ain't Nothin' But A Hound Dog", "Oh, Pretty Woman", "Night Train", "Isn't It Romantic?", "Movin' Out", "I'm Your Puppet", "We Are Family", "Varsity Drag", "Funeral for a Friend", "Stairway to Heaven", "Alone Again, Naturally", "Running Scared", "Superstition", "The First Time Ever I Saw Your Face", "It's My Party", "Fever", "Hungry Like the Wolf" and "Consider Me Gone" and numerous others.
Really- every episode of the series is a testament to the love and care that the Tanners have for ALF- if they really didn't like him or love him, they would have turned him over to the Alien Task Force long ago...

I think they all loved ALF but never showed probably because ALF always did something or get into trouble. I will say I didnt think Kate really liked ALF until she hugged him goodbye in the final episode.

Well...the real actors didn't like being on "Alf". Once the last ep aired, everyone left. No goodbyes...nothing!