Both are fine and get the point across. Two small errors
1. 日本語を話せますが、流暢ではありません。 change わ to は
2. 日本語を少し話せます。 don't need the に
If you are emphasizing that you only speak a little Japanese, you might also use
3. 日本語を少ししか話せません。
It's similar to #2 above, but as indicated it emphasize that you only speak a little Japanese. Sort of like the difference between "I speak a bit of Japanese" and "I only speak a little bit of Japanese".