The show method does what you're looking for.
For example, given the following dataframe of 3 rows, I can print just the first two rows like this:
df = sqlContext.createDataFrame([("foo", 1), ("bar", 2), ("baz", 3)], ('k', 'v'))
df.show(n=2)
which yields:
+---+---+
| k| v|
+---+---+
|foo| 1|
|bar| 2|
+---+---+
only showing top 2 rows