Some people care about performance, and ABCL is nowhere near SBCL in this regard.
I also don't know if ABCL's compiler is offline (generating class files from CL code) or on-demand (likely using OW2 ASM). While it is no longer impossible to do, it remains tricky to generate Dalvik bytecode at runtime, and the performance hit is significant (look at Clojure on Android).
I would have thought that ABCL (Armed Bear CL) would be a more suitable candidate for porting to Android. It's already written in Java.