A fixup of http://stackoverflow.com/a/21138900/110151 (untested)

gistfile1.py

from functools import wraps
from fabric.api import task as _task

def fix_boolean(f):

    true_values = ("yes", "true", "1")
    false_values = ("no", "false", "0")

    def fix_bool(value):
        if isinstance(value, basestring):
            if value.lower() in false_values:
                return False
            if value.lower() in true_values:
                return True
        return value

    @wraps(f)
    def wrapper(*args, **kwargs):
        args_ = [fix_bool(arg) for arg in args]
        kwargs_ = {k: fix_bool(v) for k,v in kwargs.iteritems()}
        return f(*args_, **kwargs_)

    return wrapper


def task(*args, **kwargs):
    if args:
        return _task(fix_boolean(args[0]), *args[1:], **kwargs)
    else:
        return lambda fn: _task(fn, **kwargs)