150 Gallons is quite a big pond for two small goldies (they are small right?). I think you will be fine for some time as long as you do not over feed them or have excess foods polluting the water. Comparing to the alternative, (living in the fish bowl) I think they will do pretty good. Common gold fishes are cold blooded. So in general they will not have any problem living outside as long as it is not freezing. I would suggest holding off until water is atleast 50 degrees or more.
The filters are not that expensive. Depending on your budget you can buy submersible filter quite cheap. Take a look at this site:
http://www.bigalsonline.com/BigAlsUS/ctl36...aster1000filterI usually buy from that store and they are pretty good in all sorts of pond related stuff. You may also look into ebay.
Good luck !