Gee, I wonder who Jazz could be referring to.
Dussel, you do realize that Manuel Antonio and Arenal are 2 different areas, don't you? Because that's not clear from the way you worded your question. I'll assume you meant to ask about them seperately since you say you've been "there some years ago". I think you'll find things have changed considerably in both areas since you were last there with prices and options up considerably. Also you didn't specify when you were going and whether it would be just you or you and a "traveling companion". Chica friendliness is not really a factor since there really isn't anything to pick up locally and if you bring a "friend" she will be checking in with you as a guest (at double room rates). Many hotels charge the same for 1 or 2 guests, but others charge $10 or more dollars more, so that whether you're traveling with another can make a difference which hotels fall into your price range. More than that, already high room rates can sky rocket when peak season hits, but the rate of increase can vary considerably as can how they define peak season dates. For this analysis, I'll assume you have a companion and that you're traveling during the low season (which ends in only 1-2 months).
The
http://www.arenal.net website that Jazz mentioned is a great source of info for the Fortuna/Arenal area. A lot of guys around here (including myself) think highly of Los Lagos
http://www.hotelloslagos.com but that may be a bit beyond your price range. The Arenal Paraiso is another place that gets good reviews and is well located and is only $70/nt ($80/nt after 12/1). The Arenal Springs Resort at $87 could be another good bet in your price range ($107 after 12/1). The problem with any of these (and most of the hotels for that matter) is that they're now on the wrong side of the volcano for lava views (another thing that may have changed since you were last there). For a hotel room with a view in your price range, you could stay at the Arenal Lodge. Their lowest price rooms with a volcano view go for $99/nt low season dbl (a little less if you're there by yourself) but their peak season has alreadt started and thos rooms there now go for $131/nt. The Arenal Observatory Lodge probably has the best views of all their Casona rooms start as little as $45/nt but those rooms have shared bath. For a double room with queen bed, private bath and volcano view, expect to pay $103/nt ($128 after the 1st). The bigger factor if you stay there is that it is very remote and you could wind up paying quite a bit for taxi service if you don't have a car. In fact, if you don't have a car you might want to be a little closer to town than any of these places, however the hotels in town also tend to fall in a lower price range than you've been considering.
I don't know as much about the Quepos/Manuel Antonio area. I've stayed at the Villas Nicolas which were very nice and now start at $85/nt low season but those go up $30 after 12/16. I've also stayed at Hotel La Colina. I was not as impressed but it was I was staying in the cheapest $45/nt standard rooms. They also have upgraded rooms with ocean views for $80-85/nt ($20 more after the 1st). Once again the cheapest places tend to be closest to town but unlike the Fortuna area things are not as spread out and it is easy to take a local bus or taxi anywhere along the 7km road between town and the park.
As for getting to either Quepos or Fortuna, the obvious choice would be booking with Interbus through the
http://www.searchcostarica.com website. That will cost you $33.25/pp each way ($37.05 after the 1st) or close to $67-74/pp round trip for each place ($130-150 for 2). If you also go directly between Fortuna and Quepos, the total package would be in the $100-111/pp range ($200-220 for 2) . The plus is that they'll take you door to door from one hotel to the other. If you want to save some money and live a little adventurously you could take the public bus for less than $5/pp each way. For 2 of you that represents a $110-130 savings just on transport costs. The negative here is that you have to get to the right bus terminal in SJ and they'll only let you off at the bus stop in Fortuna or Quepos (ie you need to get from there to your hotel somehow on your own). The other negative is if you want to go directly between these 2 destinations since CR buses routes are not so great if you want to go anywhere other than on the way to or from the capital.
Another option for getting to Fortuna is to take a day tour there from SJ and don't return with them. Believe it or not, this can come out cheaper than Interbus if you factor in such things as the sightseeing stops they might make on the way there, the hot springs admission and the various meals that are included. There was a thread somewhere where I discussed this option thoroughly. Perhaps someone else could find it and repost it for me. You could also do something similar if you're thinking of doing any whitewater rafting during your trip as Exploradores offers the option of pick-up in SJ and drop-off in Fortuna (or vice versa) if you go on their Pacuare white water rafting trip.
There really isn't anything similar to that available for going to/from Manuel Antonio though I have had correspondence with the Calypso Tour people about doing something similar with them. The problem there is that it depends on whether they have sufficient number of people signed up coming from Quepos, but it could be worth checking out.