Android NDK includes a special version of STLport since r5, and let developers to use it by specifying a flag in Android.mk files. However, if you are developing using Makefile instead (like I do), using STLport may be a little bit complicated.
First, since the build-standalone-toolchain script of NDK (also included since r5) can only include stdc++ library into the toolchain it builds, compiling with STLport headers may lead to a list of build errors. In order to prevent this, using prebuilt compilers in the NDK ("the hard way" as described in readme) may be a better choice. In this case, you will have to take care with sysroot.
Second, developing with this special STLport has some limitations as mentioned in readme: Exception and RTTI are not supported. Remember to build every cpp source files with -fno-exceptions and -fno-rtti.